LATERALLY INSET TRAILER SKIRT and INNER WHEEL SKIRT PANEL, EACH REDUCING VEHICLE DRAG

ABSTRACT

An inner wheel skirt panel centrally located under the body of a vehicle reduces overall vehicle drag by inhibiting air from otherwise being displaced laterally inward by the passing wheels of the moving vehicle. Maintaining air to remain generally static while passing under the vehicle through the central open-space between the wheels increases the effective air pressure developed immediately behind the vehicle to reduce overall drag developed between the front and rear of the vehicle. See FIGS. 21-24.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of patent application Ser.No. 15/830,236, filed Dec. 4, 2017 by Garth L. Magee.

BACKGROUND Field

The present embodiment relates to an apparatus for the reduction ofaerodynamic drag on vehicles generally having wind-exposed wheelsmounted underneath the vehicle body, such as on large commercial trucks.

Description of Prior Art

Inherently characteristic of rotating vehicle wheels, and particularlyof spoked wheels, aerodynamic resistance, or parasitic drag, is anunwanted source of energy loss in propelling a vehicle. Parasitic dragon a wheel includes viscous drag components of form (or pressure) dragand frictional drag. Form drag on a wheel generally arises from thecircular profile of a wheel moving though air at the velocity of thevehicle. The displacement of air around a moving object creates adifference in pressure between the forward and trailing surfaces,resulting in a drag force that is highly dependent on the relative windspeed acting thereon. Streamlining the wheel surfaces can reduce thepressure differential, reducing form drag.

Frictional drag forces also depend on the speed of wind impingingexposed surfaces, and arise from the contact of air moving oversurfaces. Both of these types of drag forces arise generally inproportion to the square of the relative wind speed, per the dragequation. Streamlined design profiles are generally employed to reduceboth of these components of drag force.

The unique geometry of a wheel used on a vehicle includes motion both intranslation and in rotation; the entire circular outline of the wheeltranslates at the vehicle speed, and the wheel rotates about the axle ata rate consistent with the vehicle speed. Form drag forces arising fromthe moving outline are apparent, as the translational motion of thewheel rim must displace air immediately in front of the wheel (andreplace air immediately behind it). These form drag forces arisingacross the entire vertical profile of the wheel are therefore generallyrelated to the velocity of the vehicle.

As the forward profile of a wheel facing the direction of vehicle motionis generally symmetric in shape, and as the circular outline of a wheelrim moves forward at the speed of the vehicle, these form drag forcesare often considered uniformly distributed across the entire forwardfacing profile of a moving wheel (although streamlined cycle rims canaffect this distribution somewhat). This uniform distribution ofpressure force is generally considered centered on the forward verticalwheel profile, and thereby in direct opposition to the propulsive forceapplied at the axle, as illustrated in FIG. 17.

However, as will be shown, frictional drag forces are not uniformlydistributed with elevation on the wheel, as they are not uniformlyrelated to the speed of the moving outline of the wheel rim. Instead,frictional drag forces on the wheel surfaces are highly variable anddepend on their elevation above the ground. Frictional drag must beconsidered separate from form drag forces, and can be more significantsources of overall drag on the wheel and, as will be shown, thereby onthe vehicle.

Vehicles having wind-exposed wheels are particularly sensitive toexternal headwinds reducing propulsive efficiency. Drag force on exposedwheels increases more rapidly on upper wheel surfaces than on vehicleframe surfaces, causing a non-linear relation from rising wind speedsbetween net drag forces on vehicle frame surfaces versus net drag forceson vehicle wheel surfaces.

Since upper wheel surfaces are moving against the wind at more than thevehicle speed, the upper wheel drag forces contribute more and more ofthe total vehicle drag as external headwinds rise. Thus, as externalheadwinds rise, a greater fraction of the net vehicle drag is shiftedfrom vehicle frame surfaces to upper wheel surfaces.

Moreover, upper wheel drag forces must be overcome by a propulsivecounterforce applied at the axle. Such propulsive counterforces suffer amechanical disadvantage against the upper wheel drag forces, since eachnet force is applied about the same pivot point located at the bottomwhere the wheel is in stationary contact with the ground. Thismechanical advantage that upper wheel drag forces have over propulsivecounterforces further augments the effective vehicle drag that exposedupper wheels contribute under rising headwinds. As a result of thesemagnified effects of upper wheel drag on resisting vehicle propulsion,vehicle drag is more effectively reduced by reducing the aerodynamicpressure on the upper wheel surfaces while leaving the lower wheelsurfaces exposed to impinging headwinds.

Furthermore, shielding the lower wheel surfaces can cause a net increasein vehicle drag, and a loss in propulsive efficiency. Not only does thepropulsive counterforce applied at the axle have a mechanical advantageover the lower wheel drag forces, but shielding the lower wheel surfacesusing a deflector attached to the vehicle body shifts the drag forcefrom being applied at the lower wheel to an effective higher elevationat the axle, thereby negating any mechanical advantage of a propulsivecounterforce applied at the axle has over the lower wheel drag force. Asa result, aerodynamic trailer skirts in widespread use today areunnecessarily inefficient, since they generally extend below the levelof the axle.

Nevertheless, extended height trailer skirts have been shown to improvepropulsive efficiency, since they reduce the aerodynamic pressure on theupper wheel surfaces, which cause the vast majority of wheel drag andvirtually all of the loss in vehicle propulsive efficiency due to wheeldrag. However, the extended skirts shown in the art also impact theaerodynamic pressure on the lower wheel surfaces, where propulsivecounterforces delivered at the axle have a mechanical advantage overlower wheel drag forces.

As mentioned, diverting wind from impinging on the lower wheel surfacesactually increases overall vehicle drag, reducing propulsive efficiency.Deflecting wind from impinging on these lower wheel surfaces transfersthe aerodynamic pressure from these slower moving surfaces alsosuffering a mechanical disadvantage, to faster moving vehicle bodysurfaces having no mechanical advantage over propulsive counterforces,thereby increasing vehicle drag.

Nevertheless, numerous examples in the art demonstrate the currentpreference for aerodynamic skirts extending to below the level of theaxle. For example, in U.S. Pat. No. 7,942,471 B2, US 2006/0152038 A1,U.S. Pat. No. 6,974,178 B2, U.S. Pat. No. 8,303,025 B2, U.S. Pat. No.7,497,502 B2, U.S. Pat. No. 8,322,778 B1, U.S. Pat. No. 7,806,464 B2, US2010/0066123 A1, U.S. Pat. No. 8,342,595 B2, U.S. Pat. No. 8,251,436 B2,U.S. Pat. No. 6,644,720 B2, U.S. Pat. Nos. 5,280,990, 5,921,617,4,262,953, 7,806,464 B2, US 2006/0252361 A1, U.S. Pat. No. 4,640,541 allmake no mention of the differing relationships between upper wheel dragforces and lower wheel drag forces affecting vehicle propulsiveefficiency. Most of these patents depict FIGS. showing skirts extendingwell below the level of the axle. And an examination of leading trailerskirt manufacturers shows the prevalence for extended height skirtscurrently for sale and needed to meet California carbon emissionrequirements.

Furthermore, a recent in-depth wind tunnel study sponsored the USDepartment of Energy and conducted at a pre-eminent research institutionof the United States government, Lawrence Livermore Laboratory waspublished Mar. 19, 2013, “Aerodynamic drag reduction of class 8 heavyvehicles: a full-scale wind tunnel study”, Ortega, et. al, and concludedthat trailer skirts are one of the most effective means to reduce dragon large tractor-trailer trucks. A large number of trailer skirtconfigurations were tested in this study, which employed traditionaltechniques for measuring total drag on the vehicle. Due to the nonlineareffects of upper wheel drag in rising headwinds, such techniques canproduce inaccurate measurements of gains in propulsive efficiency forvehicles having wheels exposed to headwinds. Thus, as yet this importantrelationship of upper wheel drag more predominately affecting overallvehicle drag—and especially over lower wheel drag which is oftencomparatively negligible and suffers a mechanical disadvantage againstpropulsive counterforces applied at the axle—has gone unrecognized.

And in the patent art cited above, several patents such as U.S. Pat.Nos. 4,262,953, 4,640,541, US 2006/0252361 A1, U.S. Pat. No. 7,806,464B2, U.S. Pat. No. 8,322,778 and others depict wind-deflecting panelsgenerally spanning the lateral width of the trailer, thereby inducingunnecessary drag by blocking air otherwise funneled between the wheels.Funneled air into the rear of the vehicle can reduce pressure drag onthe vehicle. In the art, there are numerous other examples of devicesattempting to enhance this vehicle drag reducing effect.

Also in the cited art above, several patents such as US 2010/0066123 A1,U.S. Pat. No. 8,342,595 B2 and U.S. Pat. No. 8,251,436 B2 depict winddeflecting panels where aligned in front of the wheels of the trailerextending to well below the level of the axle, thereby inducingunnecessary vehicle drag by transferring drag from the slower movinglower wheel surfaces having a mechanical disadvantage, to the fastermoving vehicle body and frame surfaces. And in the art, there arenumerous other examples of devices attempting to enhance this wheel dragreducing effect.

And in the art, several attempts have been made to reduce the pressuredrag induced on the body of the vehicle. For example, the oscillatingsystem in U.S. Pat. No. 9,487,250—intended to reduce pressure drag onthe vehicle itself—introduces considerable complexity over more commonfixed drag-reduction means, since it generally includes a movingdiaphragm that must be tuned for the specific operating configuration ofthe vehicle. And the oscillating mechanism is generally attached at therear of the trailer, behind the rear wheels.

And the adjustable skirts in U.S. Pat. No. 9,440,689, as well as theskirts in U.S. Pat. No. 8,783,758, both being located rearward of thetrailer wheel assembly, do not induce air to flow in-between the trailerwheels to yield a reduction in pressure drag on the vehicle. Instead,the aforementioned skirts prevent air flow from flowing laterally underthe body of the vehicle. For example, as disposed the combination of thedual adjustable skirts of U.S. Pat. No. 9,440,689 directs air away fromthe ‘pocket’ of air formed immediately behind the trailer. And theskirts of U.S. Pat. No. 8,783,758 prevent air from flowing laterallyinward under the rearmost portion of the trailer body.

And many trailer skirts in the art are generally disposed largely alongthe lateral sides of the trailer, and therefore do not substantiallyinduce air to flow generally in-between the wheel sets to thereby reducepressure drag on the trailer body. Indeed, early configurations oftrailer skirts were often disposed wholly along the outer lateral sidesof the trailer body. However, more recent configurations include theforwardmost ends thereof being disposed slightly inset toward thelongitudinal centerline of the vehicle body, since it has been foundthrough testing that this outwardly slanted configuration furtherdecreases overall vehicle drag.

As taught by prior inventions by the present applicant, one reason forthis somewhat better performance is due to this outwardly slantedconfiguration providing improved shielding of the trailing wheels fromimpinging headwinds. And as discussed herein, in order to minimizevehicle drag, it is critically important to shield the uppermost portionof otherwise exposed wheels from headwinds, while leaving lowermostwheel surfaces exposed to headwinds. The slanted skirts—extendinglaterally outwards toward the rear—generally partially shield the upperwheels, but also shield much of the lower wheels, thereby not optimallyminimizing drag on the vehicle. And these outwardly slanted skirts alsopresent a serious liability issue for trucks, since the outwardlydirected skirts divert substantial amounts of air outward that candestabilize adjacent cyclists—especially bicycle riders—from passingtrucks.

With the numerous embodiments for shielding open wheels of thevehicle—which include prior inventions by the present applicant in U.S.Pat. No. 9,567,016 as well as in U.S. Pat. No. 9,796,430—teaching thecritical importance of specifically shielding the critical drag-inducingupper wheel using a minimal drag-inducing wheel fairing, only furtherreinforces in the art the preference by skilled artisans for evenfurther deepening the outwardly slanting arrangement of conventionaltrailer skirts to provide even more effective shielding of the trailingwheels from headwinds. As such, skilled artisans have had no motivationto consider a contrary arrangement further exposing the rearward wheelsto headwinds, since such a contrary arrangement would be known tosubstantially increase drag on the vehicle.

For example, in U.S. Pat. No. 9,809,260 air deflectors are used in someembodiments to direct air outwards away from the undercarriagecomponents—and thereby away from generally flowing in-between the wheelsets—in order to reduce drag on these components. As such, it hasremained generally unappreciated in the art that any increased draginduced on these undercarriage components is often insufficient tooffset the overall drag reduction gains achievable by instead simplyredirecting substantial air to flow in-between the trailer wheel sets tothereby substantially reduce pressure drag on the vehicle.

Other previous attempts to reduce pressure drag induced on the body ofthe vehicle employed an air capture system to redirect air from thefront to the rear of the vehicle, often including air ducts. Forexample, in U.S. Pat. No. 9,527,534 air ducts are used to capture airimpinging near the front of the vehicle and communicating the thuscaptured air to rear of the vehicle through these ducts. The air ductsare generally directed either over the top or underneath the vehicle,while also generally extending rearward of the trailer wheel assembly.And such, these lengthy air ducts generally have substantialwind-exposed surface areas, introducing considerable friction dragthereon—both on surfaces thereof within and without the duct itself—tothereby limit any reduction in overall vehicle drag gained from anyreduction in pressure drag on the vehicle itself.

And in U.S. Pat. No. 9,403,563 much smaller air ducts were used on therear of the trailer, which still introduce considerable friction dragfor their relatively small size, especially when considering that thetheir smaller size severely limits the potential amount of redirectedair, thereby further limiting their effectiveness in increasing theeffective pressure developed in the relatively large volume of reducedpressure zone located immediately behind the trailer. Thus, thesesmaller air ducts redirecting smaller volumes of air also have limitedpotential to reduce the overall pressure drag on the vehicle.

For these multiple reasons, a different approach is needed to reducepressure drag on the vehicle, by using a minimal drag-inducing airdiverting means to substantially increase the effective air pressuredeveloped immediately behind the vehicle.

SUMMARY

Numerous reference embodiments for shielding open wheels of thevehicle—which include prior inventions by the present applicant in U.S.Pat. No. 9,567,016—are first presented herein, as the claimed embodimentitself can be even more effective in reducing overall vehicle drag whenused in conjunction with such upper wheel-shielding embodiments. Sinceuntil recently prior embodiments shielding the upper wheel were largelyunappreciated by those skilled in the art, the significance of both thereference and claimed embodiments may be more fully understood andappreciated when considered with a comprehensive understanding of theimportance of specifically shielding the critical drag-inducing upperwheel using a minimal drag-inducing fairing, as taught previously inU.S. Pat. No. 9,567,016—as well as in U.S. Pat. Nos. 9,878,745 and9,796,430—by the present applicant. And as a presently claimedembodiment may be more fully understood and appreciated when consideredwith a comprehensive understanding of the importance of inducing morestabilized air to flow under the central portion of the vehicle using aminimal drag-inducing air diverting means that may expose aforward-facing portion of an adjacent wheel assembly, additionalreference embodiments disposed ahead of the wheel assembly are alsopresented herein as further background in support of the use thereof incombination with a claimed embodiment.

Reference embodiments presented herein generally comprise eitherwind-diverting skirts or panels for use on vehicles having otherwisewind-exposed wheels on a wheel assembly mounted underneath the vehiclebody, such as on the trailers of large commercial trucks. Many of thereference embodiments are designed to deflect vehicle headwinds fromdirectly impinging on the upper wheel surfaces—the predominate draginducing surfaces on a wheel—and in part onto lower wheel surfaces—theleast effective drag inducing surfaces on a wheel—thereby reducingvehicle drag and increasing vehicle propulsive efficiency. Each of thesewheel shielding embodiments are also ideally designed to keep thelowermost wheel surfaces exposed to headwinds. Since propulsivecounterforces applied at the axle have a natural mechanical advantageover lower wheel drag forces, deflecting headwinds onto fully exposedlower wheel surfaces also increases vehicle propulsive efficiency.

A reference embodiment comprises an inclined aerodynamic deflector panelassembly designed to deflect headwinds otherwise impinging on upperwheel surfaces downward onto lower wheel surfaces of a trailing wheelset on either side of the wheel assembly. The deflector panel assemblycan be a generally flat panel tilted to deflect air downward onto thelower wheel surfaces, or a panel with perpendicular end platesprojection forward forming a U-shaped channel arranged to funnel airdownward onto the lower wheel surfaces. The deflector panel assemblyextends down from the vehicle body to no lower than the level of theaxle of the wheel assembly, and may included wheel skirts covering thetrailing wheel sets. The panel may also be extended across the lateralwidth of the trailer to deflect headwinds below the trailing centralaxle assembly.

A reference embodiment comprises an aerodynamic skirt panel assemblydesigned to deflect headwinds otherwise impinging on upper wheelsurfaces downward onto lower wheel surfaces of a trailing wheel set oneither side of the wheel assembly. Toward the front end, the skirt panelassembly is located substantially inboard toward the centerline of thevehicle. Toward the rear end, the skirt panel assembly diverges rapidlyto the outside of the trailing wheel set in order to divert headwinds inpart onto the lower wheel surfaces. The ideal skirt assembly extendsdown from the vehicle body to no lower than the level of the axle infront of the wheel assembly, and may include wheel skirts covering thetrailing wheel sets.

A reference embodiment comprises a method for reducing the totaldrag-induced resistive forces upon the wheel assembly as directedagainst the vehicle to reduce the required effective vehicle propulsivecounterforce.

And a further embodiment comprises a medial inner skirt panel centrallylocated substantially in-between the forward and rearward wheels of atandem wheel assembly on a semitrailer, thereby further streamlining thevehicle to reduce drag thereon. The medial inner skirt panel furtherstabilizes the generally static air passing under central axle andthrough the central tandem open-space underneath the tandem wheelassembly, further increasing the effective air pressure being developedimmediately behind the trailer to reduce drag thereon. A forward innerskirt panel located ahead of the rearward wheels of a tandem wheelassembly on a semitrailer also similarly streamlines the vehicle,reducing drag thereon. And a rearward inner skirt panel located behindthe rearward wheels of a tandem wheel assembly on a semitrailer alsosimilarly streamlines the vehicle, reducing drag thereon.

And a claimed embodiment herein comprises an inwardly disposed trailerskirt panel assembly located inset laterally toward the longitudinalcenterline of the vehicle and disposed to extend substantially forwardof the wheels of a rear wheel assembly on a semitrailer or truck. Thetrailer skirt panel assembly stabilizes the generally static air passingunder the central portion of the vehicle and under the central axlethrough the central tandem open-space underneath the tandem wheelassembly of the semitrailer or rear axle of a truck, further increasingthe effective air pressure being developed immediately behind thetrailer or truck to reduce drag thereon.

DESCRIPTION OF THE DRAWINGS

While one or more aspects pertain to most wheeled vehicles not otherwisehaving fully shielded wheels that are completely protected from oncomingheadwinds, the various embodiments can be best understood by referringto the following figures:

In FIG. 1, an inclined aerodynamic deflector panel assembly is mountedunderneath the trailer of an industrial truck in front of a wheel set ofthe rear wheel assembly and rearward of the forward landing gear.

In FIG. 2, the inclined aerodynamic wheel deflector panel assembly ofFIG. 1 is shown mounted on the trailer as viewed in cross-section fromthe front of the vehicle. Two deflector panel assemblies are shown, eachas mounted in front of one of the wheel sets of the rear wheel assembly.

In FIG. 3, an inclined aerodynamic deflector panel assembly, whichappears in side view similar to as shown in FIG. 1, is shown mounted onthe trailer as viewed in cross-section from the front of the vehicle.

In FIG. 4, a channeled aerodynamic deflector panel assembly is mountedunderneath the trailer of an industrial truck in front of the rear wheelassembly.

In FIG. 5, the channeled aerodynamic wheel deflector panel assembly ofFIG. 4 is shown mounted on the trailer as viewed in cross-section fromthe front of the vehicle. Two deflector panel assemblies are shown, eachas mounted in front of one of the wheel sets of the rear wheel assembly.

In FIG. 6, the channeled aerodynamic deflector panel assembly, whichappears in side view similar to as shown in FIG. 4, is shown mounted onthe trailer as viewed in cross-section from the front of the vehicle.

In FIG. 7, a channeled aerodynamic deflector panel and wheel skirtassembly is mounted underneath the trailer of an industrial truck infront of a wheel set of the rear wheel assembly.

In FIG. 8, an aerodynamic wheel deflector panel is mounted underneaththe trailer of an industrial truck in front of a wheel set of the rearwheel assembly.

In FIG. 9, an aerodynamic deflector panel and wheel skirt assembly ismounted underneath the trailer of an industrial truck in front of therear wheel assembly.

In FIG. 10, an aerodynamic deflector skirt assembly is mountedunderneath the trailer of an industrial truck in front of the rear wheelassembly.

In FIG. 11, the aerodynamic deflector skirt assembly of FIG. 10 is shownfrom below the vehicle.

In FIG. 12, the aerodynamic deflector skirt assembly together with awheel skirt panel assembly is mounted to the trailer of an industrialtruck.

FIG. 13 is a front cycle wheel assembly, as typically found on a bicycleor motorcycle, where a fairing is attached and positioned as shown toeach interior side of the fork assembly, thereby shielding the upper-and front-most surfaces of the spoked wheel from oncoming headwinds.

FIG. 14 is a series of curves showing the results of an analysis of thedrag mechanics on a bicycle with shielded upper wheels, indicating thata bicycle with shielded upper wheels is faster when facing headwinds.Several curves are displayed, as examples of different bicycles eachhaving a different proportion of wheel-drag to total-vehicle-drag.

FIG. 15 shows a plot of calculated average moments—about the groundcontact point—of drag force, that are exerted upon rotating wheelsurfaces as a function of the elevation above the ground. The relativedrag forces are determined from calculated wind vectors for the rotatingsurfaces on a wheel moving at a constant speed of V, and plotted forseveral different wind and wheel-surface shielding conditions.Specifically, relative magnitudes in average drag moments about theground contact point as a function of elevation are plotted, for eightconditions: comparing with (dashed lines) and without (solid lines)shielding covering the upper third of wheel surfaces, for tailwindsequal to half the vehicle speed; for null headwinds; for headwinds equalto half the vehicle speed; and for headwinds equal to the vehicle speed.The rising solid curves plotted show the highest moments to be near thetop of the wheel, while the dashed curves show the effect of the uppershield in substantially reducing the average drag moments on therotating wheel.

FIG. 16 shows a plot of calculated relative drag torque exerted uponrotating wheel surfaces as a function of elevation above the ground. Therelative total drag torques are determined from the calculated averagemoments in combination with the chord length at various elevations on awheel moving at a constant speed of V, for several different wind andwheel-surface shielding conditions. Relative magnitudes in total dragtorque about the ground contact point as a function of elevation areplotted for eight conditions: comparing with (dashed lines) and without(solid lines) shielding covering the upper third of wheel surfaces, fortailwinds equal to half the vehicle speed; for null headwinds; forheadwinds equal to half the vehicle speed; and for headwinds equal tothe vehicle speed. The areas under the plotted curves represent thetotal torque from frictional drag on wheel surfaces. Comparing thedifferences in area under the plotted curves reveals the general trendof the upper shield to substantially reduce the total drag torque on therotating wheel.

FIG. 17 (Prior Art) is a diagram of a wheel rolling on the groundrepresenting typical prior art models, showing the net pressure dragforce (P) exerted upon the forward wheel vertical profile—which moves atthe speed of the vehicle—being generally centered near the axle of thewheel and balanced against the propulsive force (A) applied at the axle.

FIG. 18 is a diagram of a wheel rolling on the ground, showing the netfriction drag force (F) upon the wheel surfaces—which move at differentspeeds depending on the elevation from the ground—being offset from theaxle and generally centered near the top of the wheel. A ground reactionforce (R)—arising due to the drag force being offset near the top of thewheel—is also shown. The force (A) applied at the axle needed toovercome the combination of drag forces (F+P) and reaction force (R) isalso shown.

In FIG. 19, an inclined aerodynamic deflector panel and wheel skirtassembly is mounted underneath the trailer of an industrial truck.

In FIG. 20, an aerodynamic wheel skirt panel 72 is shown attached theframe of a semitruck tractor. The wheel skirt panel is disposed toshield upper tire sidewalls of the rearward wheels of the truck tractorfrom headwinds otherwise impinging thereon.

In FIG. 21, a medial inner skirt panel 100 is shown in side view largelyspanning the space in-between the forward and rearward wheels of atandem wheel assembly 105 on a rearward body component of a truck orsemitrailer 101, while being further disposed laterally proximate to thelateral position of the innermost sidewalls of the wheel assembly. Arear inner skirt panel 108 is also similarly shown disposed inline withthe medial inner skirt panel, while instead extending rearward of therearmost wheel of the tandem wheel assembly. And a forward inner skirtpanel 110 is also similarly shown disposed inline with medial innerskirt panel, while instead extending ahead of the forwardmost wheel ofthe tandem wheel assembly. All panels are disposed at a laterallyinterior location near an innermost sidewall of the wheel assembly.

In FIG. 22, the inner skirt panels of FIG. 21 are shown on thesemitrailer in front view disposed inline underneath the rearward bodycomponent of a truck or semitrailer. The front view is shown as thecross sectional view A-A of FIG. 21.

In FIG. 24, the inner skirt panels of FIG. 23 are shown on the rearwardbody component of a truck or semitrailer in front view disposed inlineunderneath the rearward body component of a truck or semitrailer. Thefront view is shown as the cross sectional view A-A of FIG. 23.

In FIG. 25, inner skirt panels similar to those shown in FIG. 20 areshown instead similarly suspended underneath the frame of a semitrucktractor. The inner skirt panels are similarly disposed adjacent to theinnermost sidewalls of the respective front or rearward wheel assembly.On the front wheel assembly, the inner skirt panels are disposed withsufficient clearance apart from the tire tread to allow for directionalturning of the front wheels.

In FIG. 26, a trailer skirt panel assembly 120 is shown suspendedunderneath the rearward body component of a truck or semitrailer havingan otherwise substantially headwind-exposed rearward wheel assembly. Thetrailer skirt panel assembly is disposed substantially parallel to thelateral sidewall of the vehicle body component and laterally insetsubstantially inline with the location of an innermost sidewall of thewheel assembly. The trailer skirt panel assembly ideally extendsdownward substantially below the midmost level of the axle.

In FIG. 27, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 26 isshown as viewed in cross-section from the front of the vehicle. Twotrailer skirt panel assemblies are shown, one disposed on each lateralside of the vehicle. The rearward wheel assemblies are substantiallyexposed to headwinds flowing along a lateral side of the vehicle.

In FIG. 28, a trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 26 isshown in combination with inner skirt panels 124 disposed adjacent tothe rearward wheel assembly.

In FIG. 29, a trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 26 isshown in combination with a lateral deflector panel 122 shielding theotherwise exposed uppermost portion of the trailing wheel assembly fromheadwinds flowing along the respective lateral side of the vehicle.

In FIG. 30, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 29 isshown as viewed in cross-section from the front of the vehicle. Twotrailer skirt panel assemblies are shown, each disposed on a lateralside of the vehicle, and each in combination with a lateral deflectorpanel 122 shielding the otherwise exposed uppermost portion of thetrailing wheel assembly including an outermost wheel 126. As shown,ideally the lowermost portion of the rearward wheel assemblies remainsubstantially exposed to headwinds flowing along a lateral side of thevehicle.

In FIG. 31, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in combinationwith the lateral deflector panel 122 of FIG. 29 is shown in furthercombination with inner skirt panels 124 disposed adjacent to therearward wheel assembly.

In FIG. 32, a trailer skirt panel assembly 120 is shown suspendedunderneath the rearward body component 130 of a truck or semitrailerhaving an otherwise substantially headwind-exposed rearward wheelassembly. The trailer skirt panel assembly is disposed substantiallyparallel to the lateral sidewall of the vehicle body component andlaterally inset midway toward the location of an innermost sidewall ofthe wheel assembly. The trailer skirt panel assembly ideally extendsdownward substantially below the midmost level of the axle.

In FIG. 33, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 32 isshown as viewed in cross-section from the front of the vehicle. Twotrailer skirt panel assemblies are shown, one disposed on each lateralside of the vehicle. The rearward wheel assemblies are substantiallyexposed to headwinds flowing along the respective lateral side of thevehicle.

In FIG. 34, a trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 32 isshown in combination with inner skirt panels 124 disposed adjacent tothe rearward wheel assembly. The trailer skirt panel assembly 120extends rearward a sufficient distance to inhibit substantial lateralair flow under the vehicle.

In FIG. 35, a trailer skirt panel assembly 120 as similarly suspendedunderneath the rearward body component 130 of a truck or semitrailer asin FIG. 32 is shown instead in combination with a lateral deflectorpanel 122 shielding an otherwise exposed uppermost portion of thetrailing wheel assembly from headwinds flowing along the respectivelateral side of the vehicle.

In FIG. 36, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 35 isshown as viewed in cross-section from the front of the vehicle. Twotrailer skirt panel assemblies are shown, each disposed on a lateralside of the vehicle, each in combination with a lateral deflector panel122 shielding an otherwise exposed uppermost portion of the trailingwheel assembly. As shown, ideally a lowermost portion of the rearwardwheel assemblies remain substantially exposed to headwinds flowing alonga lateral side of the vehicle.

In FIG. 37, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 29 or35 is shown as viewed from the lateral side of the vehicle.

In FIG. 38, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer as shown insimilar combination with the lateral deflector panels 122 of FIG. 35 isfurthermore shown in further combination with inner skirt panels 124disposed adjacent to the rearward wheel assembly.

In FIG. 39, a trailer skirt panel assembly 120 is shown suspendedunderneath the rearward body component 130 of a truck or semitrailerhaving an otherwise substantially headwind-exposed rearward wheelassembly. The trailer skirt panel assembly is disposed substantiallyparallel to the lateral sidewall of the vehicle body component andlaterally inset substantially inline with the location of an innermostsidewall of the wheel assembly. The trailer skirt panel assembly ideallyextends downward substantially below the midmost level of the axle. Thetrailer skirt panel assembly is shown in combination with a slanteddeflector panel 122 shielding the otherwise exposed uppermost portion ofthe trailing wheel assembly.

In FIG. 40, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in combinationwith the slanted deflector panel in FIG. 39 is shown in furthercombination with inner skirt panel 124 disposed adjacent to the rearwardwheel assembly.

In FIG. 41, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 40 isshown as viewed from the lateral side of the vehicle.

In FIG. 42, a trailer skirt panel assembly 120 is shown suspendedunderneath the rearward body component 130 of a truck or semitrailerhaving an otherwise substantially headwind-exposed rearward wheelassembly. The trailer skirt panel assembly is disposed substantiallyparallel to the lateral sidewall of the vehicle body component andlaterally inset midway toward the location of an innermost sidewall ofthe wheel assembly. The trailer skirt panel assembly ideally extendsdownward substantially below the midmost level of the axle. The trailerskirt panel assembly is shown in combination with a slanted deflectorpanel 122 shielding an otherwise exposed uppermost portion of thetrailing wheel assembly.

In FIG. 43, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 42 isshown as viewed from the lateral side of the vehicle.

In FIG. 44, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in combinationwith the slanted deflector panel 122 in FIG. 42 is shown in furthercombination with inner skirt panel 124 disposed adjacent to the rearwardwheel assembly.

In FIG. 45, a trailer skirt panel assembly 120 is shown suspendedunderneath the rearward body component of a truck or semitrailer havingan otherwise substantially headwind-exposed rearward wheel assembly. Thetrailer skirt panel assembly is disposed substantially non-parallel to alateral side of the vehicle body component 130 and extends from near thevehicle landing gear 128 rearward and inward toward an intermediatelongitudinal position that is laterally inset substantially furthertoward the lateral location of an innermost sidewall of the wheelassembly. The trailer skirt panel assembly is shown in combination witha slanted deflector panel 122 shielding an otherwise exposed uppermostportion of the trailing wheel assembly and in further combination withinner skirt panel 124 disposed adjacent to the rearward wheel assembly.The trailer skirt panel assembly ideally extends downward substantiallybelow the midmost level of the axle.

In FIG. 46, a trailer skirt panel assembly 120 is shown suspendedunderneath the rearward body component 130 of a truck or semitrailerhaving an otherwise substantially headwind-exposed rearward wheelassembly. The trailer skirt panel assembly is disposed non-parallel tothe lateral sidewall of the vehicle body component and extends from nearthe vehicle landing gear 128 rearward and outward toward an intermediatelongitudinal position that is laterally inset from the location of anoutermost sidewall of the wheel assembly a substantial distance that isequal to less than half the lateral width of the wheel assembly. Thetrailer skirt panel assembly is shown in combination with a slanteddeflector panel 122 shielding the otherwise exposed uppermost portion ofthe trailing wheel assembly and with inner skirt panel 124. The trailerskirt panel assembly ideally extends downward substantially below themidmost level of the axle.

In FIG. 47, a trailer skirt panel assembly 120 is shown suspendedunderneath the rearward body component 130 of a truck or semitrailerhaving a substantially headwind-exposed rearward wheel assembly. Thetrailer skirt panel assembly is disposed non-parallel to the lateralsidewall of the vehicle body component while extending from near thevehicle landing gear 128 rearward and inward to an intermediate locationthat is laterally inset beyond the lateral middle of the wheel assemblysubstantially toward the lateral position of an innermost sidewall ofthe wheel assembly. From near this intermediate location the trailerskirt panel assembly further extends rearward substantially parallel tothe innermost sidewall of the wheel assembly. The trailer skirt panelassembly also ideally extends downward substantially below the midmostlevel of the axle.

In FIG. 48, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 47 isshown as viewed from the lateral side of the vehicle.

In FIG. 49, a trailer skirt panel assembly 120 is shown suspendedunderneath the rearward body component 130 of a truck or semitrailerhaving an otherwise substantially headwind-exposed rearward wheelassembly. The trailer skirt panel assembly is disposed non-parallel tothe lateral sidewall of the vehicle body component while extending fromnear the vehicle landing gear 128 rearward and inward to an intermediatelocation that is laterally inset beyond the lateral middle of the wheelassembly substantially toward the lateral position of an innermostsidewall of the wheel assembly. From near this intermediate location thetrailer skirt panel assembly further extends rearward substantiallyparallel to the innermost sidewall of the wheel assembly. The trailerskirt panel assembly is also shown in combination with slanted deflectorpanel 122 shielding an otherwise exposed uppermost portion of thetrailing wheel assembly. The trailer skirt panel assembly is also shownin further combination with inner skirt panel 124 disposed adjacent tothe rearward wheel assembly. The trailer skirt panel assembly ideallyextends downward substantially below the midmost level of the axle.

In FIG. 50, the trailer skirt panel assembly 120 as suspended underneaththe rearward body component 130 of a truck or semitrailer in FIG. 49 isshown as viewed from the lateral side of the vehicle.

In FIG. 51, the inner skirt panels 110 together with wheel deflectorpanels 122 are shown disposed on the reward body component of a cargotruck 200.

In FIG. 52, the trailer skirt panel assembly 120 together with innerskirt panel 110 and wheel deflector panel 122 is shown disposed on thereward body component of a tractor-trailer. However, the combinationshown could also represent as disposed on a cargo truck, absent thevehicle landing gear 128.

DESCRIPTION OF WHEEL DRAG MECHANICS

As mentioned, drag force on exposed wheels increases more rapidly onupper wheel surfaces than on vehicle frame surfaces, causing anon-linear relation from rising wind speeds between net drag forces onvehicle frame surfaces versus net drag forces on vehicle wheel surfaces.Thus, vehicles having wind-exposed wheels are particularly sensitive toexternal headwinds reducing propulsive efficiency. As a result, thereexists a need for an improved aerodynamic deflector and skirt for use onindustrial trucks and trailers.

Because of this rising dominance of wheel drag in rising headwinds—dueto the non-linear relation from rising wind speeds between net dragforces on vehicle frame surfaces versus net drag forces on vehicle wheelsurfaces—a discussion of the wheel drag mechanics central to thisnon-linear relationship is presented herein. The upper wheel fairing isdescribed below as a simple solution for reducing vehicle drag in risingheadwinds on a cycle, and is presented herein as background for thepresent embodiment.

The shielding provided by fairing 1 in FIG. 11 is particularly effectivesince aerodynamic forces exerted upon exposed vehicle surfaces aregenerally proportional to the square of the effective wind speedimpinging thereon. Moreover, the power required to overcome these dragforces is generally proportional to the cube of the effective windspeed. Thus, it can be shown that the additional power required toovercome these drag forces in propelling a vehicle twice as fast over afixed distance, in half the time, increases by a factor of eight. Andsince this power requirement is analogous to rider effort—in the case ofa bicycle rider—it becomes critical to shield the most criticaldrag-inducing surfaces on a vehicle from oncoming headwinds.

FIG. 14 shows the results of an analysis of the drag mechanics on abicycle with shielded upper wheels. The curves indicate that a bicyclewith shielded upper wheels is faster when facing headwinds. Moreover,the gains in propulsive efficiency are shown to quickly increase in onlya modest headwind, but continue to rise as headwinds increase further.

In any wheel used on a vehicle, and in the absence of any externalheadwinds, the effective horizontal wind speed at a point on the wheelat the height of the axle is equal to the ground speed of the vehicle.Indeed, the effective headwind speed upon any point of the rotatingwheel depends on that point's current position with respect to thedirection of motion of the vehicle.

Notably, a point on the moving wheel coming into direct contact with theground is necessarily momentarily stationary, and therefore is notexposed to any relative wind speed, regardless of the speed of thevehicle. While the ground contact point can be rotating, it is nottranslating; the contact point is effectively stationary. And points onthe wheel nearest the ground contact point are translating with onlyminimal forward speed. Hence, drag upon the surfaces of the wheelnearest the ground is generally negligible.

Contrarily, the topmost point of the wheel assembly (opposite theground) is exposed to the highest relative wind speeds: generally atleast twice that of the vehicle speed. And points nearest the top of thewheel are translating with forward speeds substantially exceeding thevehicle speed. Thus, drag upon the surfaces of the upper wheel can bequite substantial. Lower points on the wheel are exposed to lessereffective wind speeds, approaching a null effective wind speed—and thusnegligible drag—for points nearest the ground.

Importantly, due to the rotating geometry of the wheel, it can be shownthat the effective combined frictional drag force exerted upon the wheelis typically centered in closer proximity to the top of the wheel,rather than centered closer to the axle as has been commonly assumed inmany past analyses of total wheel drag forces. While the net pressure(or form) drag (P) force on the forwardly facing profile of the wheel isgenerally centered with elevation and directed near the axle on thewheel (as shown in FIG. 17), the net frictional drag force (F) upon themoving surfaces is generally offset to near the top of the wheel (asshown in FIG. 18).

Indeed, it is near the top of the wheel where the relative winds areboth greatest in magnitude, and are generally oriented most directlyopposed to the forward motion of rotating wheel surfaces. Moreover, inthe absence of substantial external headwinds, the frictional dragexerted upon the lower wheel surfaces contributes relatively little tothe net drag upon the wheel, especially when compared to the drag uponthe upper surfaces. The combined horizontal drag forces (from pressuredrag from headwinds deflected by both the leading and trailing wheelforwardly facing profiles, and from frictional drag from headwindsimpinging upon the forwardly moving surfaces) are thus generallyconcentrated near the top of the wheel under typical operatingconditions. Moreover, with the faster relative winds being directedagainst the uppermost wheel surfaces, total drag forces combine near thetop to exert considerable retarding torque upon the wheel.

As mentioned, the horizontal drag forces are primarily due to bothpressure drag forces generally distributed symmetrically across theforwardly facing vertical profiles of the wheel, and to winds infrictional contact with moving surfaces of the wheel. Pressure dragforces arise primarily from the displacement of air from around theadvancing vertical profile of the wheel, whose circular outline moves atthe speed at the vehicle. As discussed above, since the entire circularprofile moves uniformly at the vehicle speed, the displacement of airfrom around the moving circular profile is generally uniformlydistributed with elevation across the forwardly facing vertical profileof the wheel. Thus, these pressure drag forces (P, as shown in FIG. 17and FIG. 18) are also generally evenly distributed with elevation acrossthe entire forwardly facing vertical profile of the wheel, and centerednear the axle. And these evenly distributed pressure drag forces arisegenerally in proportion only to the effective headwind speed of thevehicle.

Frictional drag forces (F, as shown FIG. 18), however, are concentratednear the top of the wheel where moving surfaces generally exceed vehiclespeed—while the lower wheel surfaces move at less than the vehiclespeed. Since drag forces are generally proportional to the square of theeffective wind speed, it becomes apparent that with increasing windspeed, that these upper wheel frictional drag forces directed upon themoving surfaces increase much more rapidly than do pressure drag forcesdirected upon the forward profile of the wheel. Indeed, these frictiondrag forces generally arise in much greater proportion to an increasingeffective headwind speed of the vehicle. Nevertheless, these increasedfrictional drag forces being directed on the upper wheel is only apartial factor contributing to augmented wheel drag forces beingresponsible for significantly retarded vehicle motion.

Significantly, both types of drag forces can be shown to exert momentsof force pivoting about the point of ground contact. And as such, eithertype of drag force exerted upon the upper wheel retards vehicle motionconsiderably more than a similar force exerted upon a substantiallylower surface of the wheel. Minimizing these upper wheel drag forces istherefore critical to improving propulsive efficiency of the vehicle.

Also important—and due to the rotating geometry of the wheel—it can beshown that the vehicle propulsive force on the wheel appliedhorizontally at the axle must substantially exceed the net opposing dragforce exerted near the top of the wheel. These forces on a wheel areactually leveraged against each other, both pivoting about the samepoint—the point on the wheel which is in stationary contact with theground—and which is constantly changing lateral position with wheelrotation. Indeed, with the geometry of a rolling wheel momentarilypivoting about the stationary point of ground contact, the lateral dragand propulsive forces each exert opposing moments of force on the wheelcentered about this same point in contact with the ground.

Furthermore, unless the wheel is accelerating, the net torque from thesecombined moments on the wheel must be null: The propulsive momentgenerated on the wheel from the applied force at the axle mustsubstantially equal the opposing moment from drag forces centered nearthe top of the wheel (absent other resistive forces, such as bearingfriction, etc.). And the propulsive moment generated from the appliedforce at the axle has a much shorter moment arm (equal to the wheelradius) than the opposing moment from the net drag force centered nearthe top of the wheel (with a moment arm substantially exceeding thewheel radius)—since both moment arms are pivoting about the samestationary ground contact point. Thus, for these opposing moments toprecisely counterbalance each other, the propulsive force applied at theaxle—with the shorter moment arm—must substantially exceed the net dragforce near the top of the wheel.

In this way, the horizontal drag forces exerted upon the upper surfacesof the wheel are leveraged against opposing and substantially magnifiedforces at the axle. Hence, a relatively small frictional drag forcecentered near the top of the wheel can have a relatively high impact onthe propulsive counterforce required at the axle. Shielding these upperwheel surfaces can divert much of these headwind-induced drag forcesdirectly onto the vehicle body, thereby negating much of the retardingforce amplification effects due to the pivoting wheel geometry.

Moreover, since the propulsive force applied at the axle exceeds thecombined upper wheel drag forces, a lateral reaction force (R, as shownin FIG. 18) upon the wheel is necessarily developed at the groundcontact point, countering the combined unbalanced propulsive and dragforces on the wheel: Unless the wheel is accelerating, the reactionforce at the ground, together with the upper wheel net drag forces(F+P), combine (A=F+R+P, as shown in FIG. 18) to countervail the lateralpropulsive force (A) applied at the axle. This reaction force istransmitted to the wheel through frictional contact with the ground. Inthis way, an upper wheel drag force is further magnified against theaxle. For these multiple reasons, it becomes crucial to shield the upperwheel surfaces from exposure to headwinds.

Given that the propulsive force (A) applied at the axle must overcomeboth the net wheel drag forces (F+P) and the countervailing lowerreaction force (R) transmitted through the ground contact point, it canbe shown that the net drag force upon the upper wheel can oppose vehiclemotion with nearly twice the sensitivity as an equivalent drag forceupon the static frame of the vehicle. Hence, shifting the impact ofupper wheel drag forces to the static frame can significantly improvethe propulsive efficiency of the vehicle.

Furthermore, as drag forces generally increase in proportion to thesquare of the effective wind speed, the more highly sensitive upperwheel drag forces increase far more rapidly with increasing headwindspeeds than do vehicle frame drag forces. Thus, as the vehicle speedincreases, upper wheel drag forces rapidly become an increasingcomponent of the total drag forces retarding vehicle motion.

And given the greater sensitivity of speed-dependent upper wheel dragforces—as compared against vehicle frame drag forces—to the retarding ofvehicle motion, considerable effort should first be given to minimizingupper wheel drag forces. And shielding the faster-moving uppermostsurfaces of the wheel assembly from oncoming headwinds, by using thesmallest effective fairing assembly, is an effective means to minimizeupper wheel drag forces.

Contrarily, drag forces on the lower wheel generally oppose vehiclemotion with reduced sensitivity compared to equivalent drag forces onthe static frame of the vehicle. Propulsive forces applied at the axleare levered against lower wheel drag forces, magnifying their impactagainst these lower wheel forces. Shielding lower wheel surfaces cangenerally negate this mechanical advantage, and can actually increaseoverall drag on the vehicle.

Moreover, as discussed above, headwinds on the static frame generallyexceed the speed of winds impinging on the lower surfaces of the wheel.Hence, frictional drag forces on the lower wheel surfaces are greatlyreduced. Thus, it is generally counterproductive to shield the wheelbelow the level of the axle. Drag on a vehicle is generally minimizedwith upper wheel surfaces shielded from headwinds and with lower wheelsurfaces exposed to headwinds.

Wheel drag sensitivity to retarding vehicle motion becomes even moresignificant in the presence of external headwinds. With externalheadwinds, the effective wind speed impinging on the critical upperwheel surfaces can well exceed twice the vehicle speed. Shieldingprotects the upper wheel surfaces both from external headwinds, and fromheadwinds due solely to vehicle motion.

Indeed, wheel surfaces covered by the shield are exposed to winds duesolely to wheel rotation; headwinds are deflected. The effective dragwinds beneath the shield are generally directed tangentially to rotatingwheel surfaces, and vary in proportion to radial distance from the axle,reaching a maximum speed at the wheel rim equal to the vehicle speed,regardless of external headwinds. Since drag forces vary generally inproportion to the square of the wind speed, the frictional drag forcesare considerably reduced on shielded upper wheel surfaces. Using thesewind shields, shielded wheel surfaces are exposed to substantiallyreduced effective wind speeds—and to generally much less than half ofthe drag forces without shielding.

Diminished drag forces from external headwinds impinging on the slowermoving lower surfaces of a rolling wheel generally oppose wheel motionwith much less retarding torque than drag forces from winds impinging onthe faster upper surfaces. Indeed, tests demonstrate that with uppershields installed on a suspended bicycle wheel, the wheel will spinnaturally in the forward direction when exposed to headwinds. Withoutthe shields installed, the same wheel remains stationary when exposed toheadwinds, regardless of the speed of the headwind. And an unshieldedspinning wheel will tend to stop spinning when suddenly exposed to aheadwind. This simple test offers an explanation for the unexpectedresult and demonstrates that by minimally shielding only the upper wheelsurfaces from external headwinds, the overall drag upon the rotatingwheel can be substantially reduced.

Furthermore, as external headwinds upon a forwardly rotating vehiclewheel add relatively little frictional drag to the lower wheelsurfaces—which move forward at less than the vehicle speed—but add farmore significant drag to the upper wheel surfaces, which move forwardfaster than the vehicle speed and which can more significantly retardvehicle motion, shielding the upper wheel surfaces against headwinds isparticularly beneficial. Since drag forces upon the wheel are generallyproportional to the square of the effective wind speed thereon, and theadditional drag on the wheel—and thereby on the vehicle—increasesrapidly with headwinds, shielding these upper surfaces greatly reducesthe power required to propel the vehicle. Moreover, the relativeeffectiveness of shielding upper wheel surfaces generally increases withincreasing headwinds.

An examination of the retarding wind vectors on a rotating wheel canreveal the large magnitude of drag retarding moments upon the uppermostwheel surfaces, relative to the lower wheel surfaces. And an estimate ofthe frictional drag torque on the wheel can be determined by firstcalculating the average moments due to drag force vectors at variouspoints—all pivoting about the ground contact point—on the wheel (resultsshown plotted in FIG. 15), and then summing these moments at variouswheel elevations above the ground and plotting the results (FIG. 16).The area under the resulting curve (shown in FIG. 16 as a series ofcurves representing various headwind conditions) then represents thetotal frictional drag (absent profile drag) torque upon the wheel.

In order to determine the relationship between this torque and elevationon the wheel, the magnitudes of the drag wind vectors that areorthogonal to their corresponding moment arms pivoting about the pointof ground contact must first be determined. These orthogonal vectorcomponents can be squared and then multiplied by the length of theircorresponding moment arms, in order to determine the relative momentsdue to drag at various points along the wheel rim.

The orthogonal components of these wind vectors tend to increaselinearly with elevation for points on the rim of the wheel, and also forpoints along the vertical mid-line of the wheel. Calculating the momentsalong the vertical mid-line of the wheel can yield the minimum relativedrag moments at each elevation. Calculating an average of the maximumdrag moment at the rim combined with the minimum drag moment along themid-line can then yield the approximate average drag moment exerted ateach elevation upon the wheel. Multiplying this average drag moment bythe horizontal rim-to-rim chord length can yield an estimate of the dragtorque exerted upon the wheel at each elevation level (FIG. 16). Thesecalculations are simply determined from the geometry of the rotatingwheel; the object of this analysis is to determine the likely relativemagnitudes of drag torques upon the wheel at various elevations.

From the resulting plots (FIG. 16), it can be estimated that theuppermost approximate one-third section of the wheel likely contributesmost of the overall drag torque upon the wheel. Thus, by shielding thisupper section from headwinds, drag torque can be considerably reduced.With upper-wheel shielding, as noted above, the relative winds beneaththe shield are due mostly to wheel rotation, and are generally directedtangentially to the wheel. The resulting drag torque under the shieldedsections can then be determined as above, and compared with theunshielded drag torque for similar headwind conditions.

These calculations—generally confirmed by tests—indicate a substantialreduction in retarding drag torque upon the shielded upper wheelsurfaces. In the absence of external headwinds, the plots of FIG. 16indicate that shielding the uppermost approximate one-third section ofthe wheel can reduce the drag torque of this section considerably, by asmuch as 75 percent. Moreover, repeating calculations and testing with anexternal headwind equal to the vehicle speed indicates that upper wheelshielding can reduce the comparative upper wheel drag torque of thissection by still more, perhaps by as much as 90 percent. Hence, thepotential effectiveness of shielding upper wheel surfaces can besignificant, especially with surfaces having higher drag sensitivities,such as wheel spoke surfaces.

As discussed above, since upper wheel drag forces are leveraged againstthe axle—thereby magnifying the propulsive counterforce required at theaxle—an increase in drag force on the wheels generally retards vehiclemotion much more rapidly than does an increase in other vehicle dragforces. And while under external headwind conditions, the total drag ona vehicle with wheels exposed directly to headwinds increases still morerapidly with increasing vehicle speed.

Shielding upper wheel surfaces effectively lowers the elevation of thepoint on the wheel where the effective net drag force is exerted,thereby diminishing the magnifying effect of the propulsive counterforcerequired at the axle, as discussed above. As a result, the reduction indrag force upon the vehicle achieved by shielding the upper wheelsurfaces is comparatively even more significant with increasing externalheadwinds. Shielding these upper wheel surfaces can thereby improverelative vehicle propulsion efficiency under headwinds by an evengreater margin than under null wind conditions.

Moreover, shielding these upper wheel surfaces can be particularlybeneficial to spoked wheels, as round spokes can have drag sensitivitiesmany times greater than that of more streamlined surfaces. As roundspokes—in some configurations—can have drag coefficients ranging fromone to two orders of magnitude greater than corresponding smooth,streamlined surfaces, shielding the spokes of the upper wheel fromexternal wind becomes particularly crucial in reducing overall drag uponthe wheel.

Accordingly—given these multiple factors—a relatively small streamlinedfairing attached to the vehicle structure and oriented to shield theupper surfaces of the wheel assembly from oncoming headwindssubstantially reduces drag upon the wheel, while minimizing total dragupon the vehicle. Consequently, an embodiment includes the addition ofsuch a fairing to any wheeled vehicle—including vehicles having spokedwheels, where the potential drag reduction can be even more significant.

The addition of such minimal fairings to each side of a traditionalspoked bicycle wheel, for example, reduces windage losses and improvespropulsive efficiency of the bicycle, particularly at higher cyclespeeds or in the presence of headwinds, while minimizing cycleinstability due to crosswind forces. Since crosswinds are a significantfactor restricting the use of larger wheel covers, minimizing thefairing size is also an important design consideration. And minimizingform drag induced by the forward-facing profile of the fairing also willinfluence the fairing design. The preferred fairing size will likelysubstantially cover the upper section of the exposed wheel, and beplaced closely adjacent to the wheel surfaces, consistent with generaluse in bicycles. In heavier or powered cycles, design considerations maypermit somewhat larger fairings, covering even more of the wheelsurfaces.

As shielding upper wheel surfaces can reduce overall drag on thevehicle, while simultaneously augmenting the total frontal profile areaof the vehicle exposed to headwinds, a natural design constraint emergesfrom these competing factors: Shields should be designed sufficientlystreamlined and positioned sufficiently close to wheel surfaces toprovide reduced overall vehicle drag. And as shielding effectivenesspotentially increases under headwind conditions, shields designed withlarger surface areas and larger frontal profiles may still providereduced overall vehicle drag under headwind conditions, if not undernull wind conditions. Thus, a range of design criteria may be applied toselecting the best configuration and arrangement of the fairing, andwill likely depend on the particular application. In any particularapplication, however, the embodiment will include a combination ofdesign factors discussed above that will provide a reduction in overallvehicle drag.

In a cycle application, for example, fairings positioned within thewidth of the fork assembly will likely provide the most streamlineddesign which both shields spokes from headwinds but also minimizes anyadditional form drag profile area to the vehicle frame assembly. Inother applications, insufficient clearances may preclude positioning thefairings immediately adjacent to moving wheel surfaces. In suchsituations, headwinds may be sufficient in magnitude to cause areduction in overall vehicle drag to justify the use of wider upperwheel fairings—positioned largely outside the width of the forkassembly—with extended forward profile areas.

Furthermore, from the previous analysis a consideration the drag torquecurves wholly above the level of the axle, it becomes apparent thatshielding the wheel is best centered about an elevation likely between75 and 80 percent of the diameter of the wheel, or near the center ofthe area under the unshielded torque curve shown in FIG. 16. While dragforces are generally greatest in magnitude near the top of the wheel,the effective exposed topmost surface areas are much smaller, therebylimiting the magnitude of drag torques upon the uppermost surfaces ofthe wheel. Thus, the upper wheel fairing would best extend above andbelow this critical level (generally, between 75 and 80 percent of thediameter of the wheel) in order to optimally minimize drag upon thewheel. And as the surfaces forward of the axle are the first to beimpacted by headwinds, shielding these surfaces is essential todeflecting headwinds from the rearward surfaces. Thus, thehigher-sensitivity drag-inducing surfaces in the forward upper quadrantand centered about this critical elevation on the wheel generally needto be shielded for optimal minimization of drag. Thesehigher-sensitivity drag-inducing surfaces generally centered about thiscritical elevation and extending to include those surfaces with higherdrag-inducing sensitivities that are positioned mostly in the forwardupper quadrant of the wheel, but likely also to include much of thewheel surfaces positioned in the rearward upper quadrant, are hereindefined and later referred to as: major upper drag-inducing surfaces.And the critical level about which the major drag-inducing surfaces aregenerally centered in elevation is herein defined and later referred toas: critical elevation.

As discussed, the precise elevation about which the major upperdrag-inducing surfaces are centered, as well as the precise extent towhich surfaces in the forward quadrant and in the upper half of thewheel are included in the major upper drag-inducing surfaces, willdepend on the particular application and operating conditions. Certainwheel surfaces with higher drag sensitivities, such as wheel spokes,generally need to be shielded when positioned within the region of themajor upper drag-inducing surfaces. Other surfaces such as smooth tiresurfaces having lower drag sensitivities may also benefit from shieldingif their surface areas are extensive, are positioned near the criticallevel in elevation, or are the primary upper wheel surfaces exposed toheadwinds. In the example analysis of FIGS. 15 and 16, a uniform surfaceacross the wheel having a constant drag-sensitivity was assumed. In anyparticular application, the unique combination of different wheelsurfaces with differing drag sensitivities will determine the particularheight of the critical elevation level about which the major upperdrag-inducing surfaces are centered.

A similar analysis can be performed for form drag forces on the movingforward vertical profiles of the wheel rim or tire. The results obtainedare generally similar in form, though may differ somewhat in magnitudesas the effective wind speeds on the moving profiles are generally loweron the upper wheel—equal to the vehicle speed—and will depend on theparticular application, including the total area of the wheel forwardprofile exposed to headwinds, and to headwind and vehicle speeds.Nevertheless, the net pressure drag torque caused by the moving outlineof the wheel is also centered above the level of the axle, and therebymerits consideration in determining the particular height of thecritical elevation level, and in the ultimate configuration of thefairing.

Hence, the fairing shown in FIG. 13 is best configured to shield theuppermost and forward wheel surfaces, and to extend rearward to at leastpartially shield the forward profile of the trailing portion of theupper wheel rim, consistent with the further requirement to extenddownward as much as practical to the level of the axle. As mentioned,crosswind considerations will also influence the ultimate configurationfor a particular application.

In consideration of further embodiments described below, the operatingprinciples described above will generally apply, and may be referredthereto.

DETAILED DESCRIPTION

Various wheel-shielding reference embodiments are first described belowin detail, each providing means to deflect headwinds from directlyimpinging on the upper wheel surfaces and partially onto the lower wheelsurfaces of a trailing wheel assembly, thereby reducing vehicle drag andincreasing propulsive efficiency. A first present embodiment ispresented comprising an inner skirt panel disposed under a semitrailerand arranged to stabilize the air passing under central axle and throughthe central open-space within the tandem wheel assembly. And finally, asecond present embodiment is then presented comprising an inwardlydisposed trailer skirt panel assembly located substantially insetlaterally toward the longitudinal centerline of the vehicle and disposedto extend substantially forward of the wheels of a rearward wheelassembly disposed on a semitrailer or truck.

First Reference Embodiment—FIGS. 1 and 2

As shown in FIGS. 1 and 2, a reference embodiment comprises an inclinedaerodynamic wheel deflector panel assembly 20 attached to and mountedunderneath the body of a trailer 16 for a commercial vehicle. Theinclined wheel deflector panel assembly 20 is located forward of therear wheel assembly 17 and located directly in front of a trailing wheelset 18 which would otherwise be exposed to headwinds when the vehicle isin forward motion. The inclined wheel deflector panel assembly 20 isplanar in shape, mounted inclined in a forwardly-angled orientation withthe upper edge more forwardly located and the lower surface located morerearward on the vehicle. The inclined wheel deflector panel assembly 20spans the lateral width of the trailing wheel set 18 of the trailingrear wheel assembly 17 located on either side of the vehicle. Theoptimal inclined wheel deflector panel assembly 20 extends downwardideally to no lower than the level of the axle 19 and is locatedproximal to the trailing wheel set 18 in order to deflect upper wheelheadwinds onto the exposed lower wheel surfaces.

It can be concluded from the discussion of wheel drag mechanics above,that since propulsive counterforces applied to the wheel at the axlehave a mechanical advantage over lower wheel drag forces—which arenecessarily applied to the wheel below the level of the axle—directingupper wheel headwinds onto the lower wheel surfaces can significantlyreduce overall vehicle drag and improve propulsive efficiency. Thereasons for these gains in vehicle efficiency become apparent by furtherconsidering how wheel drag forces compare with vehicle body drag forces.

As discussed earlier, drag forces on the wheel must be countered by apropulsive force from the vehicle body applied at the axle. And it canbe established that drag forces on the upper wheel have a mechanicaladvantage over countervailing propulsive counterforces applied at theaxle. And with the wheel deflector assembly attached to the vehiclebody, drag on the deflector must also be countervailed by a propulsivecounterforce applied to the vehicle body at a propulsive axle.

Thus, in order to determine the relative difference in total vehicledrag between the traditional extended height deflector divertingheadwinds from impinging on both the upper and the lower wheels, and theimproved reduced height deflector with the lower wheel surfaces ideallyfully exposed to headwinds, the added vehicle drag derived from thesurface of the deflector panel extending below the level of the axlemust be compared against the vehicle drag arising from the correspondingadditional surfaces of the lower wheel otherwise shielded by theextended deflector. And as already established above, the relativeeffects of these resistive forces on vehicle propulsion are non-linearlyrelated, and vary considerably with increasing headwinds: for vehiclesfacing faster external headwinds the nonlinear effects quickly increase,as discussed above and as shown in FIG. 14, where the results of ananalysis of the drag mechanics of a bicycle facing increasing headwindsshows rapid increases in propulsive efficiency by shielding the upperwheels.

A skilled artisan will recognize from the curves shown FIG. 14 that asthe relative external headwind increases on the vehicle, so does theincrease in propulsive efficiency of the vehicle. And a skilled artisanwill also recognize that the natural design constraint described abovefor the cycle wheel fairing of FIG. 13 similarly applies to the winddeflecting fairing of the present embodiment.

This inherent design constraint implies that for a given vehicle under agiven relative external headwind condition—as shown along the horizontalaxis of the plots in FIG. 14—a wind-deflecting fairing of the presentembodiment will similarly be constrained to have a limited overallwind-deflecting extent that will produce a reduction in overall vehicledrag. This limited wind-deflecting extent includes a limit on the totaldrag-inducing surface area extent of the wind-deflecting fairing,including a combined limit in both forward and downward extension offairing surfaces.

And as discussed extensively above for the cycle wheel fairing of FIG.13, the relative effects of drag forces on the fairing versus drag onthe various points on the wheel are not simply related. Instead, thedrag forces on various points on the wheel are magnified or de-magnifiedas applied against the axle, whereas the drag on either the cyclefairing or on the similar drag-inducing surfaces of the wind-deflectingfairing of the present embodiment are directly applied equivalentlyagainst the same axle.

Thus, since propulsive counterforces applied at the axle have amechanical advantage over drag forces on the lower wheel surfaces, asimple comparison of the net drag force on either surface alone—eitheron the lower wheel or on the extended deflector surface—is entirelyinsufficient to determine the relative effect each has on vehiclepropulsive efficiency. Instead, the magnitudes of the drag force fromeach surface must be reflected to an equivalent force applied at thesame axle and compared against one another.

For the lower wheel surfaces, the net drag force as applied against theaxle is diminished by leveraging about the point of ground contact, aspreviously discussed. For the lower deflector panel surface, the dragforce is directed against the axle without magnification since it istransmitted directly through the body and frame of the vehicle. Althoughanother axle of the vehicle may be the used as the propulsive axle, thetwo net drag forces must be compared against each other as reflected atthe same affected axle in order to gauge their relative effects onoverall vehicle drag.

For the lower deflector surface, the drag force on the surface is—likeother vehicle body drag forces—directly countervailed by the propulsivecounterforce applied at the driven axle. For the lower wheel surfaces,the situation is more complicated due both to the mechanical advantagethat the propulsive forces have over lower wheel drag forces, and to theeffects that the summation moments of drag force (FIG. 15) at differentpoints on the rotating wheel have on the net lower wheel drag force.

As noted earlier under the Description of Wheel Drag Mechanics, and asshown in the plot of FIG. 16, the average drag torque exerted againstthe lower wheel surfaces has far less impact on the total wheel drag asexerted upon the vehicle than does the average drag torque exertedagainst the upper wheel surfaces. This is due largely to the pivotinggeometry of the rotating wheel, where wheel forces are levered about thesame stationary point of ground contact at the bottom of the wheel.Owing in part to their longer moment arms, drag forces applied to theupper wheel produce far greater resistive torques on the wheel than dodrag forces applied to the lower wheel.

Consequently, drag forces on the upper wheel surfaces are ideallyshifted to the lower wheel surfaces in order to benefit the propulsiveefficiency of the vehicle. As a result, deflecting headwinds from theupper wheel surfaces onto the lower wheel surfaces can substantiallyreduce overall vehicle drag and improve propulsive efficiency.

And in the case of industrial trucks having large wheels with largertires, the relative effects of resistive pressure drag forces on thewheel over frictional drag forces is exacerbated over that of a spokedbicycle wheel as described above in the discussion of the wheel dragmechanics. As mentioned, the spoked wheels with thin tires and rims usedon a bicycle can produce significant frictional drag effects resistingvehicle propulsion. Trucks with smooth wheels and tires are moresignificantly affected by pressure drag forces acting against the upperwheel forward-facing profile surfaces, than are bicycles with thin tiresand rims.

Thus for trucks, deflecting upper wheel headwinds downward onto thelower wheel becomes an important operating function. Since propulsivecounterforces at the axle have a mechanical advantage over lower wheeldrag forces applied to the wheel below the level of the axle, deflectingheadwinds downward onto the lower wheel can reduce overall vehicle dragand improve propulsive efficiency.

The natural design constraint method discussed above can also be used incombination with an accounting for the non-linear effects on vehicledrag from drag forces directed on various points on the wheel todetermine the limited extent of the wind-deflecting fairing of thepresent embodiment that will also yield an overall reduction in vehicledrag, including the combined limit in both forward and downward extentof the fairing. And as is evident from the curves of FIG. 14, thecombined limit for the overall drag-inducing extent of thewind-deflecting fairing of the present embodiment will vary with bothvehicle configuration and relative external headwind condition.

From an examination of the curves of FIG. 14, it becomes evident thatthe worst-case limit for the overall extent of the fairing is while thevehicle is operated under null wind conditions, where the relative gainsin vehicle efficiency are comparatively minimal, and as shown at theleft vertical axis of the plots of FIG. 14. As the relative externalheadwind increases, the relative gains in vehicle efficiency quicklyincrease, as shown in the general trend of the efficiency curves risingtoward the right side of the plots.

Therefore, a skilled artisan then will understand that the mostrestrictive limit for the overall extent of the fairing will be whilethe vehicle is operated under null external headwinds conditions. If theextent of the fairing is sufficiently limited to produce an overallreduction in vehicle drag under null operating conditions, then the thuslimited fairing will also produce even more gains in vehicle efficiencyunder an external headwind condition.

And from the discussion above, it becomes evident that the fairing couldbe designed either to be more limited in forward extent and moreextensive in downward extent or alternatively could be designed insteadto be more extensive in forward extent and more limited in downwardextent, and still produce the same measure of gains in overall vehiclepropulsive efficiency.

Thus, the fairing could be designed to be somewhat limited in forwardextent and to extend somewhat below the level of the axle while stillyielding a reduction in overall vehicle drag, especially while thevehicle is operated under a substantial relative external headwindcondition. This potential configuration for the fairing becomes quiteevident both from an examination of the curves of FIG. 16, and from aconsideration of how the very limited mechanical disadvantage thatsurfaces of the wheel located not very far below the level of the axlehave over vehicle frame drag forces, such as wheel fairing or deflectordrag forces.

Indeed, FIG. 16 shows that near the level of the axle, much lessrelative gains in propulsive efficiency are gained from shielding morecentrally located wheel surfaces in elevation than from shielding theuppermost wheel surfaces positioned substantially above the axle nearthe critical elevation. And FIG. 16 also shows that the relative gainsin vehicle efficiency increase in rising relative external headwinds.

While the ideal configuration of the fairing includes a limit forfairing surfaces to extend downward to lower than the level of the axle,the discussion above makes clear that this is optimal limitation is notfully restrictive. Instead, a skilled artisan would recognize that awind-deflecting fairing of the present embodiment could be designed tobe somewhat limited in forward extent while also extending somewhatbelow the level of the axle while still yielding a reduction in overallvehicle drag, especially while the vehicle is operated under a varietyof relative external headwind conditions.

Or alternatively, a wind-deflecting fairing of the present embodimentcould be designed to be more extensive in forward extent, while beingsomewhat limited in extending to no lower than the level of the axle,while still yielding a reduction in overall vehicle drag, especiallywhile the vehicle is operating under a variety of relative externalheadwind conditions. Thus, a variety of configurations for extending thesurfaces of the wind-deflecting fairing of the present embodiment isincluded that will yield an effective reduction in overall vehicle drag.

In consideration of further reference embodiments described below, theoperating principles described above will generally apply, and may bereferred thereto.

Second Reference Embodiment—FIGS. 1 and 3

As shown in FIGS. 1 and 3, a reference embodiment comprises an inclinedaerodynamic deflector panel assembly 15 attached to and mountedunderneath the body of a trailer 16 for a commercial vehicle. Theinclined deflector panel assembly 15 is located forward of the rearwheel assembly 17 and located in front of trailing wheel sets 18 whichwould otherwise be exposed to headwinds when the vehicle is in forwardmotion. The inclined deflector panel assembly 15 is planar in shape,mounted inclined in a forwardly-angled orientation with the upper edgemore forwardly located and the lower surface located more rearward onthe vehicle. The inclined deflector panel assembly 15 spans the lateralwidth of the trailer 17, and where aligned directly in front of thewheel sets 18 ideally extends downward to no lower than the level of theaxle. The inclined deflector panel assembly 15 is located proximal tothe trailing wheel assembly 18 in order to deflect headwinds onto theexposed lower wheel surfaces, and to deflect headwinds from directlyimpinging on the central axle assembly 19, thereby reducing overallvehicle drag and improving propulsive efficiency.

Third Reference Embodiment—FIGS. 4 and 5

As shown in FIGS. 4 and 5, a reference embodiment comprises a channeledaerodynamic wheel deflector panel assembly 25 attached to and mountedunderneath the body of a trailer 16 for a commercial vehicle. Thechanneled wheel deflector panel assembly 25 is located forward of therear wheel assembly 17 and located directly in front of a trailing wheelset 18 which would otherwise be exposed to headwinds when the vehicle isin forward motion. The channeled wheel deflector panel assembly 25includes a deflector plate 22 which is generally planar in shape,mounted inclined in a forwardly-angled orientation with the upper edgemore forwardly-located and the lower surface located more rearward onthe vehicle. The channeled wheel deflector panel assembly 25 includesforwardly-projecting end plates 24 attached to either side edge of thedeflector plate 22, forming a channeled deflector panel assembly 25 tofunnel headwinds directly onto the lower wheel surfaces, minimizing anyoutwardly deflected headwind from otherwise impinging on the trailingupper wheel surfaces.

The channeled wheel deflector panel assembly 25 ideally extends downwardto no lower than the level of the axle 19 and is located proximal to thetrailing wheel set 18 in order to deflect and funnel headwinds onto theexposed lower wheel surfaces, thereby reducing overall vehicle drag andimproving propulsive efficiency.

Fourth Reference Embodiment—FIGS. 4 and 6

As shown in FIGS. 4 and 6, a reference embodiment comprises a channeledaerodynamic deflector panel assembly 30 attached to and mountedunderneath the body of a trailer 16 for a commercial vehicle. Thechanneled deflector panel assembly 30 is located forward of the rearwheel assembly 17 and located in front of both trailing wheel sets 18which would otherwise be exposed to headwinds when the vehicle is inforward motion. The channeled deflector panel assembly 30 includes adeflector plate 28 which is generally planar in shape, mounted inclinedin a forwardly-angled orientation with the upper edge moreforwardly-located and the lower surface located more rearward on thevehicle. The deflector plate 28 spans the lateral width of the trailer16, and where directly aligned in front of the wheels ideally extendsdownward to no lower than the level of the axle 19. The channeleddeflector panel assembly 30 includes forwardly-projecting end plates 32attached to either side edge of the deflector plate 28, forming achanneled deflector panel assembly 30 to funnel headwinds directly ontothe lower wheel surfaces and minimize any outwardly deflected headwindfrom otherwise impinging on the trailing upper wheel surfaces. Althoughnot shown, between the wheel sets 18, the deflector plate 28 may extendfurther downward to deflect headwinds well below the central axleassembly 19.

The channeled deflector panel assembly 30 is located proximal to thetrailing wheel set 18 in order to deflect headwinds onto the exposedlower wheel surfaces, and to deflect headwinds from directly impingingon the central axle assembly 19, thereby reducing overall vehicle dragand improving propulsive efficiency.

Fifth Reference Embodiment—FIGS. 7 and 5

As shown in FIG. 7 in side view, and as shown in FIG. 5 when viewed incross-section from the front of the vehicle, a reference embodimentcomprises the channeled aerodynamic wheel deflector panel assembly 25identical to that of the third embodiment above, together with removableupper wheel skirt panels 38 covering the outside of the trailing wheelsets 18. The upper wheel skirt panels 38 also ideally extend downward tono lower than the level of the axle 19.

The upper wheel skirt panels 38 extend from the deflector plate 22rearward to cover adjacent trailing wheel sets 18, thereby shielding thetrailing upper wheels from external headwinds. The channeled wheeldeflector panel assembly 25 used in combination with the upper wheelskirt panels 38 reduces overall vehicle drag and improves propulsiveefficiency.

Sixth Reference Embodiment—FIGS. 7 and 6

As shown in FIG. 7 in side view, and as shown in FIG. 6 when viewed incross-section from the front of the vehicle, a reference embodimentcomprises the channeled aerodynamic deflector panel assembly 30identical to that of the fourth embodiment above, together withremovable upper wheel skirt panels 38 covering the outside of thetrailing wheel sets 18. The upper wheel skirt panels 38 also ideallyextend downward to no lower than the level of the axle 19.

The upper wheel skirt panels 38 extend from the deflector plate 28rearward to cover adjacent trailing wheel sets 18, thereby shielding thetrailing upper wheels from external headwinds. The channeled deflectorpanel assembly 30 used in combination with the upper wheel skirt panels38 reduces overall vehicle drag and improves propulsive efficiency.

Seventh Reference Embodiment—FIGS. 8 and 2

As shown in FIG. 8 in side view, and as shown in FIG. 2 when viewed incross-section from the front of the vehicle, a reference embodimentcomprises an aerodynamic wheel deflector panel 45 is attached to andmounted underneath the body of a trailer 16 for a commercial vehicle.The wheel deflector panel 45 is located forward of the rear wheelassembly 17 and located in front of a trailing wheel set 18, which wouldotherwise be exposed to headwinds when the vehicle is in forward motion.The wheel deflector panel 45 is planar in shape, sufficiently wide todeflect headwinds from directly impinging on the upper wheels of thetrailing wheel set, mounted vertically and shown oriented parallel tothe axle 19. The wheel deflector panel 45 ideally extends downward nolower than the level of the axle 19, and is located proximal to thetrailing wheel set 18 in order to deflect headwinds substantially towardeither the outside or the inside of the wheel set 18, or onto the lowerwheel surfaces—thereby reducing overall vehicle drag and improvingpropulsive efficiency.

This simple wheel deflector panel configuration is appropriate for usewhen limited clearance space exists in front of the trailing wheel set.

Eighth Reference Embodiment—FIGS. 8 and 3

As shown in FIG. 8 in side view, and as shown in FIG. 3 when viewed incross-section from the front of the vehicle, a reference embodimentcomprises an aerodynamic deflector panel 50 is attached to and mountedunderneath the body of a trailer 16 for a commercial vehicle. Thedeflector panel 50 is located forward of the rear wheel assembly 17 andlocated in front of a trailing wheel sets 18 which would otherwise beexposed to headwinds when the vehicle is in forward motion. Thedeflector panel 50 is planar in shape, spans the lateral width of thetrailer 16, and where aligned directly in front of the wheel sets 18ideally extends downward to no lower than the level of the axle 19. Thedeflector panel 50 is mounted vertically and parallel to the axle 19.The deflector panel 50 is located proximal to the trailing wheel sets 18in order to deflect headwinds substantially toward either the outside ofthe trailing upper wheels, under the central axle assembly, or onto thelower wheel surfaces—thereby reducing overall vehicle drag and improvingpropulsive efficiency.

This simple deflector panel configuration is appropriate for use whenlimited clearance space exists in front of the trailing wheel assembly.

Ninth Reference Embodiment—FIGS. 9 and 2

As shown in FIG. 9 in side view, and similar to as shown in FIG. 2 whenviewed in cross-section from the front of the vehicle, a referenceembodiment comprises the aerodynamic wheel deflector panel 45 identicalto that of the seventh embodiment above, together with removable upperwheel skirt panels 42 covering the outside of the trailing wheel sets18. The upper wheel skirt panels 42 also ideally extend downward to nolower than the level of the axle 19.

The upper wheel skirt panels 42 extend from the deflector panel 45rearward to cover adjacent trailing wheel sets 18, thereby shielding thetrailing upper wheels from external headwinds. The wheel deflector panel45 used in combination with the upper wheel skirt panels 42 reducesoverall vehicle drag and improves propulsive efficiency.

This simple wheel deflector panel configuration is appropriate for usewhen limited clearance space exists in front of the wheel sets and wherethe use of exterior wheel skirts panels is permitted.

Tenth Reference Embodiment—FIGS. 9 and 3

As shown in FIG. 9 in side view, and similar to as shown in FIG. 3 whenviewed in cross-section from the front of the vehicle, a referenceembodiment comprises the aerodynamic wheel deflector panel 50 identicalto that of the eighth embodiment above, together with removable upperwheel skirt panels 42 as used in the ninth embodiment above. Thedeflector panel 50 used in combination with the upper wheel skirt panels42 reduces overall vehicle drag and improves propulsive efficiency.

This simple wheel deflector panel configuration is appropriate for usewhen limited clearance space exists in front of the wheel sets, wheredeflecting headwinds from directly impinging on the central axleassembly 19 is needed, and where the use of exterior wheel skirts panelsis permitted.

Eleventh Reference Embodiment—FIGS. 10 and 11

As shown in FIGS. 10 and 11, a reference embodiment comprises anaerodynamic vehicle skirt assembly 60 is attached to and mountedunderneath the body of a trailer 16 for a commercial vehicle. Thevehicle skirt assembly 60 is located forward of the rear wheel assembly17 which would otherwise be exposed to headwinds when the vehicle is inforward motion. The vehicle skirt assembly 60 ideally extends downwardto no lower than the level of the axle 19 of the trailing wheel set 18,leaving lower wheel surfaces of the trailing wheel set 18 exposed toheadwinds.

The vehicle skirt assembly 60 is shown mounted to the trailer 16 withthe forwardmost end of the vehicle skirt assembly 60 inset toward thecenterline of the trailer 16 to a position in general longitudinalalignment with the inside of—and thereby substantially in front of—theinnermost surface of the trailing wheel set 18. Extending rearward, thevehicle skirt assembly 60 progressively varies in position toward theoutside of the body of the trailer 16, extending more rapidly toward theoutside wheel when nearest the rear end, which is located proximate tothe trailing wheel set 18. The rear end of the vehicle skirt assembly 60is located near the outer side of the wheel set 18, thereby deflectingheadwinds substantially toward the outside of the upper wheel surfacesand below onto the lower wheel surfaces.

The vehicle skirt assembly 60 may be constructed from either a singlepanel or from multiple panels arranged end-to-end. The vehicle skirtassembly 60 may be constructed with resilient materials, especiallyalong the lower edge that may occasionally contact road obstacles. Thevehicle skirt assembly 60 may also be mounted to the trailer 16 bydeflectable resilient means, returning the vehicle skirt assembly 60 tothe proper aerodynamic position after contacting road obstacles.

Twelfth Reference Embodiment—FIG. 12

As shown in FIG. 12, a reference embodiment comprises the aerodynamicvehicle skirt assembly 60 identical to that of the eleventh embodimentabove, together with removable upper wheel skirt panels 42 covering theoutside of the trailing wheel sets 18 as used in the tenth embodimentabove.

The upper wheel skirt panels 42 extend from the aerodynamic vehicleskirt assembly 60 rearward to cover adjacent trailing wheel sets 18,thereby ideally shielding the trailing upper wheel surfaces fromexternal headwinds. The aerodynamic vehicle skirt assembly 60 used incombination with the upper wheel skirt panels 42 reduces overall vehicledrag and improves propulsive efficiency.

Thirteenth Reference Embodiment—FIG. 20

As shown in FIG. 20, a reference embodiment comprises an aerodynamicwheel skirt panel 72 disposed adjacent to an upper sidewall of a tire ofa rearward wheel assembly 74 of a semi truck tractor 70. The skirt panel72 is attached to the vehicle frame 76 and arranged to shield the uppertire sidewall from being otherwise exposed to headwinds, therebyreducing overall vehicle drag and improving vehicle propulsiveefficiency. While the tractor is shown with dual wheel assemblies 74,the skirt panel could also be utilized on a tractor having only a singlerearward wheel assembly.

First Present Embodiment—Includes FIGS. 21-24 and 51

As shown in FIGS. 21-24, a present embodiment comprises a medial innerskirt panel 100 disposed substantially in-between the forwardmostrearward wheel 102 and rearmost wheel 104 of a tandem wheel assembly 105on a rearward body component of a truck or semitrailer 101. The medialinner skirt panel 100 is ideally attached to the frame of the tandemwheel assembly 105, and is further disposed to be laterally aligned nearto the lateral position of the laterally innermost sidewall of theinnermost wheel 102 of the tandem wheel assembly. The medial inner skirtpanel 100 preferably extends from near the top of tandem assemblydownwards to substantially below the axle 106.

The medial inner skirt panel 100 provides a barrier between theotherwise intervening wheel open-space that exists in-between theforward and rearward wheels of the tandem wheel assembly, and thecentral tandem open-space that exists in-between the opposing innermostwheels of the tandem wheel assembly. So disposed, the medial inner skirtpanel 100 inhibits displacement of air molecules from exchangingin-between the intervening wheel open-space and the central tandemopen-space between the dual wheels—which is caused by the motion of thepassing wheels—thereby reducing drag on the moving vehicle.

As shown in FIGS. 21-24, another embodiment comprises a rear inner skirtpanel 108 disposed rearward of the rearmost wheel 104 of a wheelassembly on a rearward body component of a truck or semitrailer. Therear inner skirt panel 108 is attached to the frame of the tandem wheelassembly, and is further disposed to be laterally aligned near to thelateral position of the laterally innermost sidewall of innermost wheelof the tandem wheel assembly. The rear inner skirt panel 108 preferablyextends from near the top of tandem assembly downwards to generallybelow the axle 106, consistent with ground obstacle clearancerequirements.

As shown in FIGS. 21-24, another embodiment comprises a forward innerskirt panel 110 disposed ahead of the forwardmost wheel 104 of a wheelassembly on a rearward body component of a truck or semitrailer. Theforward inner skirt panel 110 is ideally attached to the frame of thetandem wheel assembly, and is further disposed to be laterally alignednear to the lateral position of the laterally innermost sidewall of theinnermost wheel of the tandem wheel assembly. The forward inner skirtpanel 110 preferably extends from near the top of tandem assemblydownwards to substantially below the axle 106, consistent with anyground obstacle clearance requirements.

And while the inward-facing surface of the rear skirt panels 108 isgenerally flat for minimal drag thereon from air passing in-between theinnermost wheels through the central tandem open-space, theoutward-facing surface thereof may be curved in a streamlined shape—forreduced drag from the laterally inward directed movement of airimpinging thereon—to provide more laminar motion of air toward therearmost portion of the panel, further reducing drag on the vehicle. Bythe further streamlining the outward facing surface for lateral airmotion, a more laminar condition of air motion immediately behind therear skirt panel 108 can be achieved, thereby further reducing drag onthe moving vehicle.

And while the inner skirt panels 100, 108 and 110 generally extendsubstantially below the axle 106, the function of the inner skirt panelsis not principally for reducing drag on the relatively low effectivevehicle-drag-inducing lower-wheel surfaces, but rather includes furtherstabilizing the generally static air passing under the central axle 106and through the central tandem open-space.

Since a static air column possesses maximum pressure therein relative toan adjacent moving air column—since moving air molecules possess acomponent of momentum force in addition to a pressure force componentthat then offsets the resistive wholly pressure force component existingwithin the adjacent static air column—a generally static air column moreeffectively connected to the rear of the vehicle can thereby transmitmaximum air pressure from the front onto the rear of the vehicle.

By further stabilizing any internal relative motion of air moleculeswithin this central air column, then maximizes the volume of static airpassing with minimal disturbance under the moving vehicle through thecentral tandem open-space, with the central air column thereby remainingin a more laminar relative flow condition as a result. With a maximallystabilized streamlined flow condition present within the central aircolumn passing under or through the center of the tandem wheel assembly,any increased air pressure developed ahead of tandem wheel assembly isthen more fully communicated through the central tandem open-space tothe rear of the vehicle at up to the speed of sound.

Any increased air pressure developed ahead of the tandem wheel assemblythen also acts to increase the amount of relative air flowing throughthe central tandem open-space to the rear of the vehicle. And as taughtabove, any increase in effective air flowing to the rear of the vehiclethen reduces the differential pressure developed between the front andrear of the moving vehicle, to thereby reduce the overall pressure dragbeing developed thereon.

Furthermore, since a function of the inner skirt panel embodiment is tostabilize the central air column passing under the vehicle, the innerskirt panels 100, 108 and 110 are best positioned laterally inward nearto the lateral position of the innermost sidewall of the innermostwheel, rather than closer to the laterally outermost tire sidewall. Sopositioned, the inner skirt panels largely prevent lateral airdisplacement within the central air column under the tandem wheelassembly by the moving wheels, thereby protecting the stability of thisair column from disturbance by the passing wheels.

If for example, the medial inner skirt panels were instead positionedlaterally near the outside of the vehicle, then the medial inner skirtpanel 100 would then allow for otherwise largely undisturbed air to beexchanged laterally from in-between the central tandem open-space thatexists in-between the opposing innermost wheels of the tandem wheelassembly, and the intervening wheel moving open-space that existsin-between the forward and rearward wheels of the moving tandem wheelassembly, thereby diminishing any vehicle drag-reducing effect from airpassing relatively undisturbed through the central open portion of thetandem wheel assembly. With the skirt panels instead positioned near theoutside of the vehicle, lateral air displacement from the outside of thevehicle to partially fill the passing void in-between the wheels isinstead diminished, thereby enhancing the flow exchange of air insteadfrom within the central air column itself to fill the passing voidin-between the wheels, thereby minimizing any vehicle drag reductionfrom stabilizing air within the central air column passing in-betweenthe wheel sets.

While the inner skirt panels are shown disposed laterally just insidethe inner sidewalls of the wheel assembly, the inner skirt panels couldalso be arranged either flush with the inner sidewalls for additionalstreamlining, or even be disposed further towards the outside of thevehicle. So disposed more towards the outermost wheel of the dual wheelassembly—rather than adjacent to the innermost sidewalls of theinnermost wheel—the medial inner skirt panel would then largely span thespace in-between the forward are rearward wheels of the tandem wheelassembly.

In a further example, as shown in FIGS. 21-24, the forward inner skirtpanel 110 shown disposed immediately ahead of the wheels may furtherenhance the stabilization of the central air column by deflecting anyair stream impinging the forwardmost wheel toward the outside of thevehicle, rather than allowing the displaced air from the wheel todisturb the central air column in front of the central axle, as would anouter forward-extending skirt panel positioned near the outside of thewheel assembly as explained above. And while shown arranged parallel tothe longitudinal centerline of the vehicle, the forward inner skirtpanel 110 could also be arranged at a converging inwardly progressingangle to enhance air flow between the innermost wheels under the tandemwheel assembly.

If arranged at an inwardly progressing convergent angle, the forwardcentral skirt panel 110 disposed on both lateral sides of the vehiclemay then form a partial open funnel to increase the relative air flowingin-between the wheels through the central tandem open-space. However, ifarranged at too steep an inwardly progressing angle, the drag induced onthe forward central skirt panel may more than offset the gains invehicle drag reduction from more air flowing in-between the wheelsthrough the central tandem open-space. Hence, a method for determiningthe proper inwardly progressing angle and overall dimension of theforward central skirt panel 110 to be used for any given vehicleoperating condition arises as a compromise between these two opposingdesign considerations. Any inwardly progressing angle of the forwardcentral skirt panel 110 must be optimized to a limited angle thatactually reduces overall vehicle drag.

And as shown in FIGS. 21-24, in another embodiment the rear inner skirtpanel 108 disposed immediately behind the wheels may further enhance airflow through the central tandem open-space by arranging the trailingpanels at an outwardly progressing angle. This diverging arrangement ofthe trailing panels may then provide for a partial open nozzleflow-accelerating effect from the expanding air exiting therefrom,thereby helping to further increase air flow through the central tandemopen-space. The outwardly progressing angle of the panels is againlimited to that which will increase the air flowing through the centraltandem open-space without either adding too much additional drag on thepanels, or reducing the transmitted air pressure gained at the rear ofthe vehicle, to offset any gains in overall vehicle drag reductionachieved therefrom. Hence, a method for determining the proper outwardlyprogressing angle and overall dimension of the rear inner skirt panel108 to be used for any given vehicle operating condition also arises asa compromise between these two opposing design considerations. Anyoutwardly progressing angle of the rear inner skirt panel 108 must beoptimized to a limited angle that actually reduces overall vehicle drag.

An even further embodiment comprises two or more of the skirt panelsconnected together to form a single streamlined panel, extending from asfar as from immediately ahead of the forwardmost wheel, rearward to asfar as immediately behind the rearmost wheel of the tandem wheelassembly. The combined panel is then arranged to accommodate verticalmotion of the axle, while largely shielding the central tandemopen-space from moving innermost wheel sidewalls and the moving spaceslocated immediately forward and rearward of the wheels, therebyproviding streamlined surfaces along the lateral sides of the centraltandem open-space to minimize any lateral disturbance of air withincentral tandem open-space by the moving wheel surfaces.

Since modern tandem wheel assemblies on trucks or semitrailers are oftenadjustable to slide longitudinally along the body of the vehicle, theinner skirt panels are often arranged to remain in a fixed positionrelative to the slidable tandem wheel assembly itself, rather than beingin a fixed longitudinal position attached directly to the underside ofthe vehicle body. Thus, the inner skirt panels can be attached directlyto the slidable tandem wheel assembly. So disposed attached to thetandem wheel assembly, the moveable inner skirt panels remain largelyeffective in stabilizing air within the central air column under themoveable tandem wheel assembly—from induced displacement by the adjacentmoving wheels—regardless of the longitudinal location of the tandemwheel assembly along the vehicle body.

However, this arrangement of inner skirt panels attached to the slidablebogey is not exclusive. The inner skirt panels could be instead attachedto the frame or body of the vehicle, or even attached together incombination with other wheel deflector or trailer skirt panels forfurther augmented reductions in vehicle drag.

Moreover, the inner skirt panels—including panel 110—also can be usefulwhile employed on other vehicles, including on cargo delivery trucks200, as shown in FIG. 51—and even on automobiles or racecars. Beingsmaller in overall surface area, cargo delivery trucks can often enjoyeven more relative drag reduction from the use of inner skirt panelsthan when used on the much larger tractor-trailers. Indeed, the vehicledrag induced by the wheels disturbing the central air column passingunder the vehicle between the rearward wheels 102 of either the smallercargo trucks 200 or even automobiles is often a much larger component ofoverall vehicle drag than is on the far larger tractor-trailers. Assuch, employing inner skirt panels on these smaller vehicles can offereven more overall vehicle drag reduction on a relative basis than onsemitrucks.

Furthermore, inner skirt panels can even be employed on the front wheelsof the vehicle, including on cargo delivery trucks, on semitrucktractors (as shown in FIG. 25), and even on automobiles, where the innerskirt panels 118 and 119 are furthermore disposed to allow for steeringmovement of the wheels. Typically, as shown in FIG. 25, thenon-horizontal edge of the inner skirt panel immediately adjacent to thewheel (disposed either in front or behind the front wheel) is preferablyconfigured either slanted or curved in shape having a curved radiussimilar to that of the front wheel, in order to allow the wheel to clearthe panel edge during vehicle turning maneuvers.

Second Present Embodiment—Includes FIGS. 26-50 and 52

As shown in various FIGS. 26-49, a further present embodiment comprisesan aerodynamic trailer skirt assembly 120 comprising one or more panelsdisposed laterally inset underneath the rearward body component 130 of atruck or semitrailer. The trailer skirt assembly 120 is shown disposedfrom a forwardmost end thereof located toward any vehicle landing gear128 that may be present on the vehicle and extending downward under thevehicle body component 130, to a rearward end thereof located near therearward wheel assembly 126. The trailer skirt assembly 120 is generallyarranged to be substantially inset laterally from the outer lateral sideof the semitrailer or truck body, and preferably arranged substantiallyparallel to the outer lateral side of the semitrailer or truckbody—although in some embodiments the rear end could be located somewhateither further inward or outward laterally from the longitudinalcenterline of the vehicle, while being disposed in sufficiently shallowconvergent or divergent angle with respect to the lateral side of thevehicle that still yields a reduction on overall vehicle drag.

Arranged generally parallel to the truck lateral side, but substantiallyinset laterally, the trailer skirt assembly 120 further stabilizes thecentral air column passing under the vehicle body from near the front ofthe truck to the rear wheel assembly, while also limiting the totalskirt assembly surface area being directly exposed to lateral-sidevehicle headwinds. By inhibiting the lateral displacement of air underthe truck body, the trailer skirt assembly 120 functions similarly tothat of the inner skirt panels 110 (see 110 of FIGS. 21-24), to maintainthe central air column passing under the vehicle in a more undisturbedstatic condition. And by arranging the trailer skirt assembly 120 to belaterally inset substantially toward the longitudinal centerline of thevehicle, thereby limits the drag induced from headwinds impinging on theextended surfaces of the trailer skirt assembly 120 itself.

And as taught above under the description of the inner skirt panels 110(FIGS. 21-24), stabilized static air contains more pressure thandisturbed, de-stabilized dynamic air. Thus, the further stabilized isthe central air column, the more effectively the higher static pressuredeveloped in the front of the vehicle is communicated directly to therear of the vehicle at up to the speed of sound, thereby actuallyincreasing the static pressure developed behind the vehicle. Andincreased air pressure developed behind the vehicle then reduces thedifferential pressure developed between the front and rear of theforward-moving vehicle, thereby decreasing overall vehicle drag.

And—as mentioned above—by arranging the trailer skirt assembly 120 to bedisposed somewhat inset laterally toward the longitudinal centerline ofthe vehicle, as shown in various FIGS. 26-50, the trailer skirt assemblyis less directly exposed to vehicle lateral-side headwinds, therebydecreasing drag induced thereon. However, arranging the trailer skirtassembly 120 to be inset laterally too far inward toward thelongitudinal centerline of the vehicle can also reduce the width of anycentral stabilized air column passing under the moving vehicle, therebyreducing the effectiveness of the trailer skirt assembly 120 incommunicating forward air pressure rearward under the vehicle to reduceoverall vehicle drag. Typically, the central open space containing thecentral air column should be substantially maintained generally as wideas the intervening space between the trailing wheel assembly 120.

Moreover, arranging the trailer skirt assembly 120 to be either inwardlyconverging or outwardly diverging from the front to the rear endsthereof, must also be arranged to be sufficiently limited in shallowangle to maintain a sufficiently wide stabilized air column passingunder the central portion of the vehicle that actually reduces overallvehicle drag.

And arranging the trailer skirt assembly 120 in too severe an inwardlyconverging or outwardly diverging angle can cause the moving trailerskirt assembly 120 to more directly impinge the otherwise generallystatic central air column, further de-stabilizing the amount ofrelatively undisturbed static air actually passing centrally under thevehicle, thereby minimizing any effectiveness of the trailer skirtassembly 120 in reducing overall vehicle drag.

And a further design consideration would likely include the vehicleoperating conditions; whether the vehicle is more often operated inwindy conditions or under more null wind conditions.

In windy conditions, the vehicle is more often exposed to more laterallydirected headwinds, thereby exposing the laterally inset trailer skirtassembly 120 itself more directly to vehicle headwinds. Thus, underwindy vehicle operating conditions, it can be beneficial to locate thetrailer skirt assembly 120 substantially more laterally inward as inFIGS. 26, 28 and 29, thereby more effectively shielding the larger skirtassembly surfaces from lateral vehicle headwinds impinging directlythereon. This may be further enhanced by angling the trailer skirtassembly 120 to be arranged slightly more inwardly convergent from thefront to the rear end thereof as in FIGS. 45, 47 and 49, but only enoughto be consistent with maintaining a sufficiently wide undisturbedstabilized central air column that actually reduces overall vehicledrag.

However, under more null wind vehicle operating conditions where vehiclelateral headwinds are more generally diverted laterally outwards tobetter shield trailer skirt assembly surfaces disposed laterally insetunder the vehicle, it can be beneficial to arrange the trailer skirtassembly 120 to progress more laterally outward divergent from the frontto rear as in FIG. 46, thereby more effectively widening and therebystabilizing the central air column toward the rear of the vehicle, whilestill being consistent with the need to minimize direct exposure of thetrailer skirt assembly surfaces to headwinds that actually reducesoverall vehicle drag. An outwardly diverging angle of the trailer skirtassembly 120 also provides less exposure of the laterally inward-facingsurfaces thereof to the central air column passing under the vehicle,thereby inducing less drag thereon and providing less disturbance to thecentral air column for enhanced stability thereof and consequentimproved vehicle drag reduction.

However, as discussed above, the inwardly converging or outwardlydiverging angle of the trailer skirt assembly 120 should be keptrelatively shallow in angle in either case, in order to maintain theeffectiveness of the trailer skirt assembly 120 in reducing overallvehicle drag. Too severe an angled arrangement of the trailer skirtassembly 120 would instead either destabilize the central air column bygenerating too much turbulence in the central air column passing underthe vehicle, or would induce too much drag on headwind-exposed surfacesof the trailer skirt assembly 120 itself, negating the potential benefitof any reduced vehicle drag by shielding the central air column fromlateral air displacement under the vehicle.

From these various design constraints, a method becomes evident foroptimally arranging the trailer skirt assembly 120 to include theseopposing factors: arrange the trailer skirt assembly 120 to be disposedsufficiently laterally outwards while extending sufficiently downwardsto inhibit substantial lateral air from flowing laterally under thevehicle that then stabilizes a sufficiently wide central air column toactually reduce overall vehicle drag, while simultaneously minimizingthe surface area of the trailer skirt assembly 120 that is substantiallyexposed to lateral vehicle headwinds, that would instead increasevehicle drag.

Thus, the trailer skirt assembly 120 would ideally extend downward asfar as practical given obstacle clearance design constraints, and as farlaterally outward as possible in order to increase the width of thestabilized central air column passing under the vehicle, while alsobeing disposed as far inwardly as possible in order to reduce the draginduced on the exposed trailer skirt assembly surfaces from vehicleheadwinds impinging thereon. Furthermore, arranging any inwardlyconverging or outwardly diverging angle of the trailer skirt assembly120 should be kept relatively shallow in angle with respect to thelateral side of the vehicle in order to reframe from furtherdestabilizing the central air column, or inducing too much drag ontrailer skirt assembly surfaces, and thereby maintain the effectivenessof the trailer skirt assembly 120 in reducing overall vehicle drag.

Given these opposing design considerations, it is likely that oneembodiment would include the trailer skirt assembly 120 disposedsubstantially parallel to the vehicle side and located laterally insetsubstantially inward toward the longitudinal centerline, with theforward end thereof located near any vehicle landing gear 128 that maybe present on the vehicle and the rear end thereof located near the rearwheel assembly. The forward end is likely located sufficiently close toany vehicle landing gear 128 in order to minimize vehicle drag.

However, this inwardly set trailer skirt assembly configurationtypically exposes the outermost wheel 126 of the rearward wheel assemblyto vehicle lateral-side headwinds, thereby substantially increasingvehicle drag, as taught by the numerous reference embodiments presentedabove. Thus, this trailer skirt assembly configuration is often bestemployed together with a rearmost wheel deflector panel 122 that isideally arranged to shield primarily the uppermost portion of the wheelsubstantially above the middle of the axle 132 from lateral vehicleheadwinds flowing along the side of the vehicle. Moreover, inner wheelskirt panels 124 would likely also be employed in combination witheither of these embodiments to further enhance vehicle drag reduction,as further illustrated in FIG. 51.

And as mentioned above, while the trailer skirt assembly 120 is showndisposed under the rearward body component 130 of a truck orsemitrailer, the trailer skirt assembly 120 could also be similarlyemployed on smaller cargo trucks or on other vehicles having sufficientground clearance located thereunder, as discussed above for the innerwheel skirt panels 110.

Advantages

From the description above, a number of advantages of someaforementioned embodiments become evident:

-   (a) An improved aerodynamic wheel set deflector panel located in    front of trailing wheels and ideally extending downward to no lower    than the axle to thereby deflect headwinds onto mechanically    disadvantaged lower wheel surfaces and to shield trailing    mechanically-advantaged upper wheel surfaces from headwinds, thereby    reduces overall vehicle drag improving propulsive efficiency.-   (b) An improved aerodynamic wheel assembly deflector panel which may    deflect headwinds below the central axle assembly, and where in    front of trailing wheels ideally extending downward to no lower than    the axle to thereby deflect headwinds onto mechanically    disadvantaged lower wheel surfaces and to shield trailing    mechanically-advantaged upper wheel surfaces from headwinds, thereby    reduces overall vehicle drag improving propulsive efficiency.-   (c) An improved aerodynamic deflector and skirt assembly where in    front of trailing wheels ideally extending downward to no lower than    the axle to thereby deflect headwinds onto mechanically    disadvantaged lower wheel surfaces and to shield trailing    mechanically-advantaged upper wheel surfaces from headwinds, thereby    reduces overall vehicle drag improving propulsive efficiency.-   (d) An improved aerodynamic vehicle skirt panel assembly ideally    extending downward to no lower than the axle to thereby deflect    headwinds onto mechanically disadvantaged lower wheel surfaces and    to shield trailing mechanically-advantaged upper wheel surfaces from    headwinds, reduces total weight of the skirt assembly, improves the    skirt ground clearance of road obstacles, and reduces overall    vehicle drag improving propulsive efficiency.-   (e) An improved aerodynamic wheel skirt panel assembly ideally    extending downward to no lower than the axle to thereby deflect    headwinds onto mechanically disadvantaged lower wheel surfaces and    to shield trailing mechanically-advantaged upper wheel surfaces from    headwinds reduces overall vehicle drag thereby improving propulsive    efficiency.-   (f) An improved aerodynamic vehicle skirt panel assembly ideally    extending downward to no lower than the axle to thereby deflect    headwinds onto mechanically disadvantaged lower wheel surfaces and    to shield trailing mechanically-advantaged upper wheel surfaces from    headwinds, reduces total weight of the skirt assembly, improves the    skirt ground clearance of road obstacles, and reduces overall    vehicle drag improving propulsive efficiency.-   (g) An inner skirt panel aligned near the lateral position of the    innermost sidewall of the innermost wheel of the tandem wheel    assembly inhibits lateral displacement of air molecules from    in-between the intervening wheel open-space and the central tandem    open-space along the axle between the wheels, thereby stabilizing    the central air column passing through the tandem wheel assembly to    reduce drag on the moving vehicle. The inner skirt panel thereby    helps stabilize the generally static air passing through the central    tandem open-space underneath the tandem wheel assembly, further    increasing the effective air pressure developed immediately behind    the trailer to reduce overall drag on the vehicle. The inner skirt    panel thereby improves vehicle propulsive efficiency by reducing the    effective overall drag on the trailer of a semitruck. Furthermore,    the inner skirt panel disposed similarly aligned adjacent to a front    wheel of a vehicle similarly reduces overall drag on the vehicle.-   (h) An inwardly disposed trailer skirt panel assembly located    substantially inset laterally toward the longitudinal centerline of    the vehicle and disposed to extend substantially forward of the    wheels of a rear wheel assembly on a semitrailer or truck. The    trailer skirt panel assembly further stabilizes the generally static    air passing under the central portion of the vehicle and under the    central axle through the central tandem open-space underneath the    tandem wheel assembly of the semitrailer or rear axle of a truck,    further increasing the effective air pressure being developed    immediately behind the trailer or truck to reduce drag thereon.

CONCLUSIONS, RAMIFICATIONS, AND SCOPE

Exposed wheels can generate considerable drag forces on a movingvehicle. These forces are directed principally near the top of thewheel, rather than being more evenly distributed across the entireprofile of the wheel. Furthermore, these upper-wheel drag forces arelevered against the axle, thereby magnifying the counterforce requiredto propel the vehicle. As a result, a reduction in drag upon the upperwheel generally enhances propulsive efficiency significantly more than acorresponding drag reduction on other parts of the vehicle.

With the net drag forces being offset and directed near the top of thewheel, nearly equivalent countervailing reaction forces—also opposingvehicle motion—are necessarily transmitted to the wheel at the ground.These reaction forces necessitate augmented down-forces to be applied inhigher speed vehicles, in order to maintain static frictional groundcontact and, thereby, vehicle traction and directional stability. Aswings and other means typically used to augment these down-forces insuch vehicles can add significant drag, it becomes evident thatsubstantial effort should be made to reduce the upper wheel drag forceson most high-speed vehicles.

Moreover, since the lower wheel drag forces suffer a mechanicaldisadvantage over propulsive counterforces, using shielding devices todeflect headwinds from impinging on lower wheel surfaces can increaseoverall vehicle drag. Given these considerations, it becomes evidentthat drag-reducing vehicle deflectors and skirts should be ideallylimited to lengths that inhibit vehicle headwinds from directlyimpinging on only the upper wheel surfaces, leaving the lower wheelsurfaces exposed.

While the embodiments shown illustrate application generally to thetrailers of industrial trucks, the embodiments could be similarlyapplied other trucks and vehicle types having wheel assemblies exposedto headwinds. And while the embodiments shown include skirt assembliesformed from relatively inexpensive flat panels, somewhat curved panelscould also be used. Further examples of alternative embodiments includehaving deflector panels mounted at various angles, all ideally limitedin height to extend downward to no lower than the level of the axle.

Although not shown, in the case where additional space exists in frontof the wheel assembly, the wheel deflector panel of the ninth embodimentcould instead be mounted in nonparallel to the axle in order to deflectwinds not only downward, but also to either side of the trailing wheelassembly.

And although not shown, the wheel skirt panel assembly of the thirteenthembodiment could further include a fender covering the front upper tiresurfaces and could also extend over the top of wheel assemblies as well.Furthermore, this embodiment could also be disposed on the rearwardwheel assemblies of the trailer as well.

In addition, the embodiments generally can include various methods ofresilient mounting to the vehicle body permitting the panels to deflectwhen impacted by road obstructions and return undamaged to their normalaerodynamic position.

And as shown, the inner skirt panel disposed toward the inside of atandem wheel assembly on a semitrailer further streamlines the vehicle,reducing drag thereon. The inner skirt panel thereby improves vehiclepropulsive efficiency by reducing drag on the trailer of a semitruck.And while shown for general use on a semitrailer, the inner skirt panelcould also be used on the rearward wheels of the tractor of a semitruck.Moreover, the inner skirt panel could also be used on smaller vehicles,such as medium-sized trucks having a single rear wheel assembly. And theinner skirt panel could even be utilized on automobiles, extendingeither in front or rearward of the wheel, ensuring that air displaced bythe wheel is directed to the outside of the wheel, rather than laterallyinward underneath the vehicle to disturb the central air column. Thus,the inner skirt panel could prove particularly beneficial when used onhigh speed racecars, requiring enhanced aerodynamic performance.

And as shown, the inwardly disposed trailer skirt panel assembly locatedsubstantially inset laterally toward the longitudinal centerline of thevehicle and disposed to extend substantially forward of the wheels of arear wheel assembly on a semitrailer or truck further streamlines thevehicle, reducing drag thereon. The trailer skirt panel assembly therebyimproves vehicle propulsive efficiency by reducing drag on a truck orthe trailer of a semitruck. And while shown for general use on a largertruck or semitrailer, the trailer skirt panel assembly could also beused in front of the rearward wheels of a smaller, single-rear-axletruck, or on smaller vehicles having sufficient ground clearance. Thus,the trailer skirt panel assembly could prove beneficial for use on avariety of different vehicle types.

Accordingly, the embodiments should not be limited to the specificexamples illustrated and described above, but rather to the appendedclaims and their legal equivalents.

Further Embodiments

-   1B. An apparatus for reducing aerodynamic drag of a terrestrial    vehicle, said vehicle having a central axle extending laterally    inwards from a rearward wheel assembly comprising one or more    wheels, with said central axle being substantially exposed to    headwinds impinging thereon while the vehicle is in forward motion,    comprising:    -   an inner skirt assembly disposed proximate to the wheel assembly        at an interior location underneath a body of the vehicle;    -   the inner skirt assembly comprising one or more panels extending        longitudinally under the vehicle body;    -   the inner skirt assembly extending laterally no further from the        lateral location of an innermost sidewall of the wheel assembly        than a distance equal to half the lateral width of the wheel        assembly;    -   any forward portion of the inner skirt assembly that is located        wholly ahead of a forwardmost said wheel assembly being aligned        at least as far from a longitudinal centerline of the vehicle        body than a trailing intermediate portion of said inner skirt        assembly, wherein the trailing intermediate portion is located        both behind the forward portion and ahead of the forwardmost        wheel assembly;    -   any rearward portion of the inner skirt assembly that is located        wholly behind a rearmost said wheel assembly being aligned at        least as far from the longitudinal centerline than a preceding        intermediate portion of said inner skirt assembly, wherein the        preceding intermediate portion is located both behind the        rearmost wheel assembly and ahead of the rearward portion; and    -   the inner skirt assembly extending downwards to at least the        level of an axis of the central axle.-   2B. The apparatus of claim 1B, further comprising:    -   the inner skirt assembly extending no further forward of a        forwardmost said wheel assembly than a distance equal to 300        percent of the diameter of said wheel assembly;    -   the inner skirt assembly extending no further rearward of a        rearmost said wheel assembly than a distance equal to 100        percent of the diameter of said wheel assembly;    -   the vehicle body is a body of a semitrailer;    -   the wheel assembly disposed on a tandem wheel assembly;    -   the tandem wheel assembly comprising a first said forwardmost        wheel assembly disposed ahead of a second said rearmost wheel        assembly; and    -   the tandem wheel assembly disposed in longitudinal slidable        attachment to the vehicle body.-   3B. The apparatus of claim 2B, further comprising:    -   the inner skirt assembly attached to the tandem wheel assembly.-   4B. The apparatus of claim 3B, further comprising:    -   the inner skirt assembly disposed ahead of the forwardmost wheel        assembly.-   5B. The apparatus of claim 3B, further comprising:    -   the inner skirt assembly disposed at a longitudinal location        midway in-between the forwardmost wheel assembly and the        rearmost wheel assembly.-   6B. The apparatus of claim 3B, further comprising:    -   the inner skirt assembly disposed behind the rearmost wheel        assembly.-   7B. The apparatus of claim 4B, further comprising:    -   the inner skirt assembly extending no further forward of the        forwardmost wheel assembly than a distance equal to 175 percent        of the diameter of said wheel assembly.-   8B. The apparatus of claim 6B, further comprising:    -   the inner skirt assembly extending no further rearward of the        rearmost wheel assembly than a distance equal to 75 percent of        the diameter of said wheel assembly.-   9B. An apparatus for reducing aerodynamic drag of a terrestrial    vehicle in forward motion, comprising:    -   an inner skirt assembly disposed proximate to a wheel of the        vehicle at an interior location underneath a body of the        vehicle;    -   the inner skirt assembly comprising one or more panels extending        longitudinally under the vehicle body;    -   the inner skirt assembly extending laterally no further from the        lateral location of an innermost sidewall of the wheel than a        distance equal to half the lateral width of the wheel;    -   any forward portion of the inner skirt assembly that is located        wholly ahead of the wheel being aligned at least as far from a        longitudinal centerline of the vehicle body than a trailing        intermediate portion of said inner skirt assembly, wherein the        trailing intermediate portion is located both behind the forward        portion and ahead of the wheel;    -   any rearward portion of the inner skirt assembly that is located        wholly behind the wheel being aligned at least as far from the        longitudinal centerline than a preceding intermediate portion of        said inner skirt assembly, wherein the preceding intermediate        portion is located both behind the wheel and ahead of the        rearward portion; and    -   the inner skirt assembly extending downwards to at least the        level of an axis of an axle of the wheel.-   10B. The apparatus of claim 9B, further comprising:    -   the inner skirt assembly extending no further forward of the        wheel than a distance equal to 125 percent of the diameter of        the wheel;    -   the inner skirt assembly extending no further rearward of the        wheel than a distance equal to 50 percent of the diameter of the        wheel; and    -   the inner skirt assembly disposed ahead of the wheel.-   11B. The apparatus of claim 9B, further comprising:    -   the inner skirt assembly extending no further forward of the        wheel than a distance equal to 125 percent of the diameter of        the wheel;    -   the inner skirt assembly extending no further rearward of the        wheel than a distance equal to 50 percent of the diameter of the        wheel; and    -   the inner skirt assembly disposed behind the wheel.-   12B. A method for reducing aerodynamic drag of a terrestrial    vehicle, said vehicle having a central axle extending laterally    inwards from a rearward wheel assembly comprising one or more    wheels, with said central axle being substantially exposed to    headwinds impinging thereon while the vehicle is in forward motion,    comprising:    -   forming an inner skirt assembly comprising one or more        aerodynamic panels;    -   attaching the inner skirt assembly to a body of the vehicle;    -   arranging the inner skirt assembly to be disposed proximate to        the wheel assembly at an interior location underneath the        vehicle body;    -   arranging the inner skirt assembly to extend longitudinally        under the vehicle body;    -   arranging the inner skirt assembly to extend laterally no        further from the lateral location of an innermost sidewall of        the wheel assembly than a distance equal to half the lateral        width of the wheel assembly;    -   arranging the inner skirt assembly wherein any forward portion        of the inner skirt assembly that is located wholly ahead of the        forwardmost wheel assembly being aligned at least as far from a        longitudinal centerline of the vehicle body than a trailing        intermediate portion of said inner skirt assembly, with the        trailing intermediate portion being located both behind the        forward portion and ahead of the forwardmost wheel assembly;    -   arranging the inner skirt assembly wherein any rearward portion        of the inner skirt assembly that is located wholly behind a        rearmost said wheel assembly being aligned at least as far from        the longitudinal centerline than a preceding intermediate        portion of said inner skirt assembly, with the preceding        intermediate portion being located both behind the rearmost        wheel assembly and ahead of the rearward portion;    -   arranging the inner skirt assembly to extend downwards to at        least the level of an axis of the central axle; and    -   arranging the inner skirt assembly to inhibit substantial        amounts of air being displaced by the moving wheel assembly from        passing laterally inwards underneath the vehicle body while the        vehicle is in forward motion.-   13B. The method of claim 12B, further comprising:    -   arranging the inner skirt assembly to extend no further forward        of a forwardmost said wheel assembly than a distance equal to        125 percent of the diameter of said wheel assembly; and    -   arranging the inner skirt assembly to extend no further rearward        of a rearmost said wheel assembly than a distance equal to 50        percent of the diameter of said wheel assembly.-   14B. The method of claim 12B, further comprising:    -   arranging the inner skirt assembly to extend no further forward        of a forwardmost said wheel assembly than a distance equal to        300 percent of the diameter of said wheel assembly;    -   arranging the inner skirt assembly to extend no further rearward        of a rearmost said wheel assembly than a distance equal to 100        percent of the diameter of said wheel assembly;    -   wherein the vehicle body is a body of a semitrailer;    -   wherein the wheel assembly is disposed on a tandem wheel        assembly;    -   wherein the tandem wheel assembly comprises a first said        forwardmost wheel assembly disposed ahead of a second said        rearmost wheel assembly; and    -   wherein the tandem wheel assembly is disposed in slidable        attachment to the vehicle body.-   15B. The method of claim 14B, further comprising:    -   arranging the inner skirt assembly to be attached to the tandem        wheel assembly. 16B. The method of claim 15B, further        comprising:    -   arranging the inner skirt assembly to be disposed ahead of the        forwardmost wheel assembly.-   17B. The method of claim 15B, further comprising:    -   arranging the inner skirt assembly to be disposed at a        longitudinal location midway in-between the first said        forwardmost wheel assembly and the second said rearmost wheel        assembly.-   18B. The method of claim 15B, further comprising:    -   arranging the inner skirt assembly to be disposed behind the        rearmost wheel assembly.-   19B. The method of claim 16B, further comprising:    -   arranging the inner skirt assembly to extend no further forward        of a forwardmost said wheel assembly than a distance equal to        175 percent of the diameter of said wheel assembly.-   20B. The method of claim 18B, further comprising:    -   arranging the inner skirt assembly to extend no further rearward        of a rearmost said wheel assembly than a distance equal to 75        percent of the diameter of said wheel assembly.-   1C. An apparatus for reducing aerodynamic drag of a tractor-trailer    combination, said combination having a rearward wheel assembly    otherwise exposed to a headwind impinging substantially unimpeded    upon an outermost upper sidewall of an outermost tire of the wheel    assembly located wholly above a level of an axis of an axle of the    wheel assembly while the tractor-trailer combination is in forward    motion, comprising:    -   an aerodynamic deflector panel assembly attached to a frame of        the tractor-trailer combination;    -   the deflector panel assembly comprising one or more panels        extending alongside and adjacent to the outermost upper        sidewall;    -   a critically aligned section of one or more of the panels        consisting of any portion thereof that is disposed immediately        adjacent to a critical vehicle-drag-inducing wheel surface of        the wheel assembly;    -   the critical wheel surface comprising a primary drag-inducing        portion of a major upper drag-inducing surface of the wheel        assembly that is centered about the level of a critical        elevation that is itself centered in elevation about the major        upper drag-inducing surface;    -   the critically aligned section spanning across the level of the        critical elevation;    -   the critical elevation being positioned not lower than a level        in elevation above the ground equal to 70 percent of the outer        diameter of the wheel assembly;    -   the critical wheel surface extending downwards nowhere lower        than a minimum level in elevation above the ground equal to 60        percent of the outer diameter of the wheel assembly; and    -   the critically aligned section extending nowhere lower than a        downward level positioned not lower in elevation above the        ground than a lowermost level that is itself located at an        elevation above the ground equal to one-third of the outer        diameter of the wheel assembly,    -   whereby the critically aligned section is disposed immediately        adjacent to the wheel assembly to divert a substantial portion        of the headwind from otherwise impinging upon the critical wheel        surface.-   2C. The apparatus of claim 1C, further comprising:    -   the tractor-trailer combination comprising at least two said        rearward wheel assemblies; and    -   wherein a first said rearward wheel assembly being disposed        immediately in front of a second said rearward wheel assembly.-   3C. The apparatus of claim 2C, further comprising:    -   the one or more panels extending alongside and adjacent to a        laterally outermost sidewall surface of a tire of each of said        rearward wheel assemblies.-   4C. The apparatus of claim 1C, further comprising:    -   the lowermost level located at the axis of the axle.-   5C. The apparatus of claim 2C, further comprising:    -   the lowermost level located at the axis of the axle.-   6C. The apparatus of claim 3C, further comprising:    -   the lowermost level located at the axis of the axle.-   7C. The apparatus of claim 1C, further comprising:    -   the lowermost level located distinctly above the axis of the        axle.-   8C. An apparatus for reducing aerodynamic drag of a semi truck    tractor, said tractor having a rearward wheel assembly otherwise    exposed to a headwind impinging substantially unimpeded upon an    outermost upper sidewall of an outermost tire of the wheel assembly    located wholly above a level of an axis of an axle of the wheel    assembly while the tractor is in forward motion, comprising:    -   an aerodynamic deflector panel assembly attached to a frame of        the tractor;    -   the deflector panel assembly comprising one or more panels        extending alongside and adjacent to the outermost upper        sidewall;    -   the deflector panel assembly disposed immediately adjacent to a        major upper drag-inducing surface of the wheel assembly; and    -   the deflector panel assembly extending nowhere lower than a        downward level positioned not lower in elevation above the        ground than a lowermost level that is itself located at an        elevation above the ground equal to one-third of the outer        diameter of the wheel assembly,    -   whereby the deflector panel assembly is disposed immediately        adjacent to the wheel assembly to divert a substantial portion        of the headwind from otherwise impinging upon the major upper        drag-inducing surface.-   9C. The apparatus of claim 8C, further comprising:    -   the tractor-trailer combination comprising at least two said        rearward wheel assemblies; and    -   wherein a first said rearward wheel assembly being disposed        immediately in front of a second said rearward wheel assembly.-   10C. The apparatus of claim 9C, further comprising:    -   the one or more panels extending alongside and adjacent to a        laterally outermost sidewall surface of a tire of each of said        rearward wheel assemblies.-   11C. The apparatus of claim 8C, further comprising:    -   the lowermost level located at the axis of the axle.-   12C. The apparatus of claim 9C, further comprising:    -   the lowermost level located at the axis of the axle.-   13C. The apparatus of claim 10C, further comprising:    -   the lowermost level located at the axis of the axle.-   14C. A method for reducing propulsory counterforces required to    countervail drag-induced resistive forces upon a tractor-trailer    combination, said combination having a rearward wheel assembly    otherwise exposed to a headwind impinging substantially unimpeded    upon an outermost upper sidewall of an outermost tire of the wheel    assembly located wholly above a level of an axis of an axle of the    wheel assembly while the tractor-trailer combination is in forward    motion, comprising:    -   forming an aerodynamic deflector panel assembly attached to a        frame of the tractor-trailer combination;    -   arranging the deflector panel assembly to comprise one or more        panels extending alongside and adjacent to the outermost upper        sidewall;    -   arranging a critically aligned section of one or more of the        panels to consist of any portion thereof that is disposed        immediately adjacent to a critical vehicle-drag-inducing wheel        surface of the wheel assembly;    -   arranging the critical wheel surface to comprise a primary        drag-inducing portion of a major upper drag-inducing surface of        the wheel assembly that is centered about the level of a        critical elevation that is itself centered in elevation about        the major upper drag-inducing surface;    -   arranging the critically aligned section to span across the        level of the critical elevation;    -   arranging the critical elevation to be positioned not lower than        a level in elevation above the ground equal to 70 percent of the        outer diameter of the wheel assembly;    -   arranging the critical wheel surface to extend downwards nowhere        lower than a minimum level in elevation above the ground equal        to 60 percent of the outer diameter of the wheel assembly; and    -   arranging the critically aligned section to be limited in        overall drag-inducing surface extension by the critically        aligned section extending no further downwards and no further        forward or rearward of the wheel assembly than to a combined        forward and rearward and downward disposition thereof so that        when taken all together while the vehicle is operated at 65 km/h        under null wind conditions any further surface extension of the        critically aligned section would further increase drag induced        thereon beyond a critical amount to cause a vehicle propulsory        counterforce itself to increase above an amount required when        the critically aligned section is otherwise absent from the        vehicle wherein the vehicle propulsory counterforce is the        propulsive force required to countervail an overall vehicle drag        force consisting of a net wheel drag force upon the wheel        assembly as magnified against the axle combined with a critical        deflector drag force induced solely from headwinds impinging        upon the critically aligned section of the deflector panel        assembly, whereby any effective reduction in drag upon said        wheel assembly as reflected through the vehicle frame and        thereby as countervailed by vehicle propulsive counterforces is        not less than the offsetting effective vehicle drag induced by        the critically aligned section itself being directly attached to        the vehicle frame and        -   whereby the deflector panel assembly can be disposed to            yield an increase in vehicle propulsive efficiency exceeding            any decrease in vehicle propulsive efficiency caused by any            increased drag on the mechanically de-magnified lower wheel            surfaces combined with any drag induced upon the critically            aligned section itself.-   15C. The method of claim 14C, further comprising:    -   the tractor-trailer combination comprising at least two said        rearward wheel assemblies; and    -   wherein a first said rearward wheel assembly being disposed        immediately in front of a second said rearward wheel assembly.-   16C. The method of claim 15C, further comprising:    -   the one or more panels extending alongside and adjacent to a        laterally outermost sidewall surface of a tire of each of said        rearward wheel assemblies.-   17C. The method of claim 14C, further comprising:    -   the lowermost level located at the axis of the axle.-   18C. The method of claim 15C, further comprising:    -   the lowermost level located at the axis of the axle.-   19C. The method of claim 16C, further comprising:    -   the lowermost level located at the axis of the axle.-   20C. The method of claim 16C, further comprising:    -   the lowermost level located distinctly above the axis of the        axle.

I claim:
 1. A method for reducing drag on a terrestrial vehicle inforward motion, said method comprising: forming an inner wheel skirtassembly that comprises: a rearmost vertical panel aligned substantiallyparallel and disposed proximate to an innermost sidewall of a laterallyinnermost wheel of a wheel assembly that is disposed wholly on onelateral side of the vehicle; the rearmost panel having a lowermost paneledge positioned no higher than a minimum panel downward level located atan elevation above the bottom of the wheel assembly equal to one-thirdthe diameter of said wheel assembly; the rearmost panel disposed whollyno further laterally from the lateral location of the innermost sidewallthan a distance equal two-thirds the lateral width of the wheelassembly; and the inner wheel skirt assembly configured wherein any flatpanels thereof are each disposed in a substantially non-horizontalorientation; and configuring the inner skirt assembly to inhibit asubstantial amount of air displaced by the forward moving wheel assemblyfrom passing laterally inside the innermost sidewall whereby when thevehicle is operated at 65 mph under null wind conditions any combinedfurther increase in the forward extension of the inner wheel skirtassembly or further decrease in the downward extension of the innerwheel skirt assembly would further increase overall vehicle drag above astandard amount otherwise induced when the inner wheel skirt assembly isotherwise absent from the vehicle.
 2. The method of claim 1, wherein,further: the minimum panel downward level is positioned no higher thanthe higher of either the bottom of a wheel rim of the wheel assembly oran elevation above the bottom of the wheel assembly equal to 25 percentof the diameter of said wheel assembly; the rearmost panel is flat; thelowermost panel edge intersects a non-horizontal rearmost panel edgethereof at a lowermost rear panel edge junction that is located forwardof the center of an axle of the wheel assembly, said lowermost rearpanel edge junction being further located at an elevation below amidmost level of the axle and horizontally no further forward from thecenter of the axle than half the diameter of the wheel assembly; thelowermost panel edge extends forward on the vehicle from the lowermostrear panel edge junction; the rearmost panel is disposed wholly nofurther laterally from the lateral location of the innermost sidewallthan a distance equal to one-third the lateral width of the wheelassembly; and the inner wheel skirt assembly is disposed wholly nofurther laterally from the lateral location of the innermost sidewallthan a distance equal to two-thirds the lateral width of the wheelassembly.
 3. The method of claim 2, wherein, further: the lowermostpanel edge is located no higher than an elevation above the bottom ofthe wheel assembly equal to 20 percent of the diameter of said wheelassembly; the rearmost panel is disposed laterally inside the laterallocation of the innermost sidewall; and the inner wheel skirt assemblyextends no further forward of the wheel assembly than a distance equalto 125 percent of the diameter of said wheel assembly.
 4. The method ofclaim 1, wherein, further: the wheel assembly is a front wheel of thevehicle
 5. The method of claim 2, wherein, further: the vehicle has arearward component of a vehicle body, said rearward body component beingsupported thereunder by the wheel assembly, with the wheel assemblyexposed to headwinds impinging upon a forward-facing lowermost portionof the wheel assembly when the vehicle is in forward motion, and withsaid forward-facing lowermost portion consisting of forward-facing wheelsurfaces spanning between the bottom of the wheel assembly and themidmost level of the axle; the rearward body component comprises a firstsubstantially rectangular vertical wall arranged along a first outermostlateral side of the vehicle; the height of the first wall is not lessthan 70 percent of the lateral width of the rearward body component; thelength of the first wall is not less than the height of the first wall;the rearward body component comprises a second vertical wall that issubstantially equal in size to the first wall, with said second wallrespectively disposed parallel thereto along an opposite outermostlateral side of the vehicle from the first side; the rearward bodycomponent comprises a horizontal top panel spanning between the upperedges of said first and second vertical walls along the respectivelengths thereof; the rearward body component comprises a continuouslyflat rectangular floor spanning between the first and second verticalwalls along the respective lengths thereof; and the flat rectangularfloor is disposed wholly above the top of the wheel assembly.
 6. Themethod of claim 5, wherein, further: the lowermost panel edge is locatedno higher than an elevation above the bottom of the wheel assembly equalto 20 percent of the diameter of said wheel assembly; and the rearwardbody component is attached to the vehicle in a permanent manner; therearmost panel is disposed laterally inside the lateral location of theinnermost sidewall; and the inner wheel skirt assembly extends nofurther forward of the wheel assembly than a distance equal to 125percent of the diameter of said wheel assembly.
 7. The method of claim6, wherein, further: the wheel assembly is aligned inline directlybehind a proximate rearward wheel on the vehicle.
 8. The method of claim6, wherein, further: the vehicle comprises a semitrailer; and thesemitrailer comprises the wheel assembly.
 9. The method of claim 8,wherein, further: the rearmost panel is disposed laterally inside thelateral location of the innermost sidewall; and the inner wheel skirtassembly extends no further forward of the wheel assembly than adistance equal to 125 percent of the diameter of said wheel assembly.10. A method for reducing drag on a terrestrial vehicle having arearward wheel assembly disposed wholly on a first lateral vehiclehalf-side positioned wholly apart from a longitudinal centerline of thevehicle, with the wheel assembly comprising a laterally outermost wheeldisposed wherein absent any other vehicle headwind-exposed panelsuspended under the vehicle immediately ahead of the wheel assembly saidoutermost wheel would be substantially exposed to headwinds impingingsubstantially unimpeded upon a forward-facing uppermost portion of theoutermost wheel when the vehicle is in forward motion, saidforward-facing uppermost portion being positioned above a midmost levelof an axle of the wheel assembly and comprising forward-facing surfacesof the outermost wheel spanning between the top of the outermost wheeland an elevation above the bottom of the outermost wheel equal to 80percent of the diameter of said outermost wheel, said method comprising:forming a trailer skirt assembly disposed wholly on the first lateralhalf-side of the vehicle that comprises: one or more contiguousnon-horizontal panels suspended under the vehicle and forward of thewheel assembly; the trailer skirt assembly furthermore disposed along amajor length thereof to be laterally inset substantially apart from arespective first outer lateral side of the vehicle; the trailer skirtassembly furthermore disposed no further from the longitudinalcenterline than a laterally outermost position located laterally insidean outer sidewall of the outermost wheel; the trailer skirt assemblyfurthermore disposed along a major length thereof to be no closer to thelongitudinal centerline than a laterally innermost position locatedlaterally no closer to the longitudinal centerline than an innersidewall of any laterally innermost wheel of the wheel assembly; thetrailer skirt assembly furthermore disposed wholly rearward of anyforward wheel of the vehicle located substantially ahead of the wheelassembly; the trailer skirt assembly furthermore disposed to extendforwards from a rearmost end thereof substantially along the length ofthe vehicle; and the trailer skirt assembly furthermore disposed toextend downwards to a lowermost level, said lowermost level beingpositioned no higher than an elevation above the bottom of the wheelassembly equal to one-third the diameter of said wheel assembly; andarranging the trailer skirt assembly to be configured properly insetlaterally from the first lateral side of the vehicle with sufficientlyextended disposition thereof to sufficiently limit lateral flow of airunder the vehicle that stabilizes a sufficiently wide central air columnpassing under a central portion of the vehicle so that while the vehicleis operated at 65 mph under null wind conditions, any furtherdestabilization of the otherwise substantially static central air columnpassing under the vehicle by otherwise arrangement of the trailer skirtassembly in combination of being either too large or small in overallwind-exposed surface area inhibiting lateral air flow under the vehicle,too widely exposed to drag-inducing lateral vehicle headwinds impingingon outer surfaces thereof, too widely exposed to drag-inducing winds ofthe central air column impinging on inward-facing surfaces thereof, orbeing too widely arranged in either convergent or divergent angleextending rearward in non-parallel disposition with respect to the firstouter lateral vehicle side, to thereby further destabilize the centralair column to a degree that would otherwise increase overall vehicledrag above a standard amount otherwise induced when the trailer skirtassembly is otherwise absent from the vehicle.
 11. The method of claim10, wherein, further: while the vehicle is operated at 65 mph under nullwind conditions, arranging the trailer skirt assembly to be configuredin an optimal arrangement that optimally limits lateral flow of airunder the vehicle to minimize overall vehicle drag to a minimal overallamount comprising reduced drag induced from winds impinging on surfacesof the trailer skirt assembly itself, whereby any deviation from saidoptimal arrangement would increase vehicle drag above said minimaloverall amount.
 12. The method of claim 10, wherein, further: thevehicle is a truck; the truck has a rearward component of a vehiclebody; the rearward body component is supported thereunder by therearward wheel assembly; the rearward body component comprises a firstsubstantially rectangular vertical wall arranged along the outermostlateral side on the first lateral vehicle half-side of the truck; theheight of the first wall is not less than 85 percent of the lateralwidth of the rearward body component; the length of the first wall isnot less than the height of the first wall; the rearward body componentfurthermore comprises a second vertical wall that is substantially equalin size to the first wall, with said second wall respectively disposedparallel thereto along an outermost lateral side on an opposite lateralvehicle half-side of the truck from the first wall; the rearward bodycomponent furthermore comprises a horizontal top panel spanning betweenthe upper edges of said first and second vertical walls along therespective lengths thereof; the rearward body component furthermorecomprises a continuously flat rectangular floor spanning between thefirst and second vertical walls along the respective lengths thereof;and the flat rectangular floor is disposed wholly above the top of thewheel assembly.
 13. The method of claim 12, wherein, further: thetrailer skirt assembly is wholly disposed laterally inset substantiallyapart from the first outer lateral side; the trailer skirt assembly iswholly disposed no further from the longitudinal centerline than thelaterally outermost position; the trailer skirt assembly is whollydisposed no closer to the longitudinal centerline than the laterallyinnermost position; the trailer skirt assembly is wholly disposed alonga major length thereof to extend downwards to at least the lowermostlevel; the lowermost level is positioned no higher than an elevationabove the bottom of the wheel assembly equal to one-quarter the diameterof said wheel assembly; the rearward body component is attached to thetruck in a permanent manner; and the trailer skirt assembly is suspendedin a vertical orientation.
 14. The method of claim 13, wherein, further:at least one said panel arranged substantially parallel to the firstouter lateral vehicle side; the lowermost level is positioned no higherthan an elevation above the bottom of the wheel assembly equal toone-fifth the diameter of said wheel assembly; and the laterallyoutermost position located no closer to the lateral location of theoutermost sidewall than a distance equal to half the lateral width ofthe wheel assembly.
 15. The method of claim 12, wherein, further: thetruck comprises a semitrailer; and the semitrailer comprises therearward body component; the trailer skirt assembly is suspended in avertical orientation; and the wind-diverting assembly is located nofurther forward on the vehicle than any vehicle landing gear legextending downward underneath the vehicle body.
 16. The method of claim15, wherein, further: the trailer skirt assembly is wholly disposedlaterally inset substantially apart from the first outer lateral side;the trailer skirt assembly is wholly disposed no further from thelongitudinal centerline than the laterally outermost position; thetrailer skirt assembly is wholly disposed no closer to the longitudinalcenterline than the laterally innermost position; the trailer skirtassembly is wholly disposed along a major length thereof to extenddownwards to at least the lowermost level; the lowermost level ispositioned no higher than an elevation above the bottom of the wheelassembly equal to one-quarter the diameter of said wheel assembly; andthe laterally outermost position located no closer to the laterallocation of the outermost sidewall than a distance equal to half thelateral width of the wheel assembly.
 17. The method of claim 16,wherein, further: at least one said panel arranged substantiallyparallel to the first outer lateral vehicle side; and the lowermostlevel is positioned no higher than an elevation above the bottom of thewheel assembly equal to one-fifth the diameter of said wheel assembly.18. The method of claim 19, wherein, further: the rearward bodycomponent is attached to the truck in a permanent manner; and thelaterally outermost position located no closer to the lateral locationof the outermost sidewall than a distance equal to half the lateralwidth of the wheel assembly.
 19. The method of claim 18, wherein,further: at least one said panel arranged substantially parallel to thefirst outer lateral vehicle side; and the lowermost level is positionedno higher than an elevation above the bottom of the wheel assembly equalto one-fifth the diameter of said wheel assembly.
 20. The method ofclaim 16, wherein, further: while the vehicle is operated at 65 mphunder null wind conditions, arranging the trailer skirt assembly to beconfigured in an optimal arrangement that optimally limits lateral flowof air under the vehicle to minimize overall vehicle drag to a minimaloverall amount comprising reduced drag induced from winds impinging onsurfaces of the trailer skirt assembly itself, whereby any deviationfrom said optimal arrangement would increase vehicle drag above saidminimal overall amount.
 21. The method of claim 1, wherein, further: thevehicle is an automobile or racecar.